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Coachwood

Scientific name

Ceratopetalum apetalum. Family: Cunoniaceae

Other names

Scented satinwood; tarwood

Description

  • Medium-size hardwood.
  • Grows straight with smooth, fragrant, greyish bark.
  • Stem has distinctive horizontal marks, or scars, which often encircle the trunk.
  • Larger trees have short buttresses.

Occurrence

  • Occurs in the central and northern coastal rainforests of New South Wales and southern Queensland.
  • Prefers gullies and creeks and often occurs in almost pure stands.

Appearance

Colour

  • Heartwood is pale pink to pinkish brown.
  • Sapwood not always distinguishable.

Grain

  • Grain is usually straight.
  • Texture is fine and even, often highly figured on the tangential face due to many bands of soft tissue.

Other

  • Wood has a characteristic caramel odour.

Uses

  • Construction: flooring.
  • Decorative: furniture and cabinetwork, interior fittings, turnery, gun stocks, carving, veneer.
  • Others: spars and masts in boat building.

Properties

  • Density: 625kg/m3 at 12% moisture content; about 1.6m3 of seasoned, sawn timber per tonne.
  • Strength groups: S5 unseasoned, SD4 seasoned.
  • Stress grades: F5, F7, F8, F11 (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: 8.1% (tangential), 4.0% (radial).
  • Unit shrinkage: 0.34% (tangential), 0.24% (radial)—these values apply to timber reconditioned after seasoning.
  • Durability above-ground: Class 4 (life expectancy less than 7 years).
  • Durability in-ground: Class 4 (life expectancy less than 5 years).
  • Lyctine susceptibility: untreated sapwood susceptible to lyctine borer attack.
  • Termite resistance: not resistant.
  • Preservation: sapwood readily impregnates with preservative, unlike the heartwood, where penetration is negligible using available commercial processes.
  • Seasoning: seasons well, some risk of internal checking; collapse is slight, so reconditioning is unnecessary.
  • Hardness: firm (rated 4 on a 6-class scale) to indent and work with hand tools.
  • Machining: machines well to a smooth surface using hand or machine tools.
  • Fixing: screws well, but tends to split when nailing; therefore, needs pre-drilling.
  • Gluing: glues well.
  • Finishing: readily accepts paint and polish; however, takes water and spirit stains better than oil stains.

Identification features

General characteristics

  • Sapwood: pink-brown.
  • Heartwood: light brown to pink-brown.
  • Texture: fine and uniform, straight grained.

Wood structure

  • Vessels: very small, visible only with lens; solitary, multiples and short radial chains.
  • Parenchyma (soft tissue): plentiful in irregularly spaced, apotracheal bands, distinct without lens.
  • Rays: fine, visible with a lens.

Other features

  • Burning splinter test: match-size splinter burns to a partial white or grey ash.
  • Figure: prominent on the back-sawn surfaces (tangential) due to bands of parenchyma.
  • Odour: obvious and characteristic, similar to caramel.

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.
  • Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
  • 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.
  • Standards Australia, 2000, AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.