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Tasmanian oak

Scientific name

Eucalyptus regnans, E. delegatensis, E. obliqua. Family: Myrtaceae

Other names

Mountain ash; Victorian ash (E. regnans); alpine ash; woolybutt (E. delegatensis); messmate stingybark; brown-top stringybark (E. obliqua)

Description

  • Large trees, grow to 90m.
  • Stem grows to 2.5m diameter at the base.
  • Trunks are free of branches to a great height.
  • Bark is rough and persistent (doesn’t shed) to the small branches on E. obliqua but only on the lower half of the trunk of the other species—above this it’s smooth.

Occurrence

  • E. regnans occurs abundantly in eastern Victoria and Tasmania.
  • E. delegatensis has a wide distribution in south eastern Australia, found at elevations of 600–900m in Tasmania and 900–1200m in Victoria.
  • E. obliqua has a wider distribution extending into parts of southern Queensland.

Appearance

Colour

  • Heartwood is pale brown to white-brown and often with pinkish tints.
  • Generally sapwood and heartwood are the same colour.

Grain

  • Generally moderately open to coarse, but even and straight.
  • Growth rings are often noticeable.

Uses

  • Decorative: furniture, linings, parquetry flooring, laminated beams, joinery, turnery.
  • Other: sawn timber in general house framing, internal flooring, joinery.

Properties

  • Density: 675-770kg/m3 at 12% moisture content; 1.3 to 1.5m3 of seasoned sawn timber per tonne.
  • Strength groups: S4 unseasoned, SD4 seasoned.
  • Stress grades: F7, F8, F11, F14 (unseasoned); F11, F14, F17, F22 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
  • Joint groups: J3 unseasoned, JD3 seasoned.
  • Shrinkage to 12% MC: E. regnans—13.3% (tangential), 6.6% (radial); E. delegatensis—8.5% (tangential), 5.2% (radial); E. oblique—11.3% (tangential), 5.1% (radial).
  • Unit shrinkage: E. regnans—0.36% (tangential), 0.23% (radial); E. delegatensis—0.35% (tangential), 0.22% (radial). E. oblique—0.36% (tangential), 0.23% (radial). These values apply to timber reconditioned after seasoning.
  • Durability above-ground: Class 3 (life expectancy 7–15 years).
  • Durability in-ground: Class 4 (life expectancy 0–5 years).
  • Lyctine susceptibility: untreated sapwood of E. delegatensis and E. obliqua is susceptible to lyctid borer attack; untreated sapwood of E. regnans is not susceptible; normally marketed as a mix of the 3 species; therefore, classed as lyctid susceptible.
  • Termite resistance: not resistant.
  • Preservation: sapwood readily impregnates with preservative, but penetration of heartwood is negligible using available commercial processes.
  • Seasoning: be careful when seasoning as prone to collapse and internal checking; also prone to surface checking on the tangential surfaces.
  • Hardness: firm to moderately hard (rated 3 and 4 on a 6-class scale) to indent and work with hand tools.
  • Machining: machines, and turns well, to a smooth surface.
  • Fixing: no difficulty using standard fittings and fastenings.
  • Gluing: bonds satisfactorily using standard procedures.
  • Finishing: readily accepts stain, polish and paint.

Identification features

General characteristics

  • Sapwood: similar to the heartwood.
  • Heartwood: pale brown to white-brown and often with pinkish tints.
  • Texture: open to moderately open; grain is usually straight; gum veins sometimes prominent in E. regnans.

Wood structure

  • Growth rings: may be prominent in E. regnans and E. delegatensis and occasionally in E. obliqua.
  • Vessels: single, medium to large in allspecies, often forming oblique chains in E. obliqua; may be more common in the early wood; tyloses vary from very few in E. regnans to common in E. obliqua; vessel lines are prominent on dressed longitudinal surfaces of all species.
  • Parenchyma (soft tissue): indistinguishable, even with a lens.
  • Rays: fine, not prominent.

Other features

  • Burning splinter test: all species burn to charcoal, sometimes with small amounts of grey or black ash.
  • Figure (pattern): generally lacking but occasionally wavy on quarter-sawn surfaces.

Research and resources

  • Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, Forest trees of Australia, 5th ed., CSIRO Publishing, Collingwood, Australia.
  • Bootle, K 2005, Wood in Australia: Types, properties and uses, 2nd ed., McGraw-Hill, Sydney.
  • Queensland Government, DAF 2018, Construction timbers in Queensland: Properties and specifications for satisfactory performance of construction timbers in Queensland. Class 1 and Class 10 buildings, Books 1 & 2, Department of Agriculture and Fisheries, Brisbane.
  • Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
  • Standards Australia, 2000, AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.