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Chengal

Scientific name

Balanocarpus heimii. Family: Dipterocarpaceae

Other names

Penak; chengai

Description

  • Straight-boled (trunk), large hardwood.
  • Grows to 25m high on good sites.

Occurrence

  • Occurs in peninsular Malaysia in a wide range of conditions from low-lying swamp flats to hills at 10,000m.
  • Limited occurrence in Thailand.

Appearance

Colour

  • Sapwood is pale yellow and well defined.
  • Heartwood is yellow to dark brown, often with a green tinge.

Grain

  • Grain is usually slightly interlocked producing a vague ribbon figure (pattern) on the radial face.
  • Even, medium texture.

Uses

  • Engineering: structural members requiring high strength and durability, railway sleepers, wharf and bridge constructions, poles, piles, mining timbers.
  • Construction: heavy duty flooring, decking.
  • Others: boat building, truck bodies, casks, vats, churns.

Properties

  • Density: 930kg/m3 at 12% moisture content; about 1.0m3 of seasoned sawn timber per tonne.
  • Strength groups: S1 unseasoned, SD2 seasoned.
  • Stress grades: F14, F17, F22, F27 (unseasoned); F17, F22, F27, F34 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
  • Joint groups: JD2 seasoned.
  • Shrinkage to 12% MC: 6.3% (tangential), 1.0% (radial).
  • Unit shrinkage: not available.
  • Durability above-ground: Class 1 (life expectancy more than 40 years).
  • Durability in-ground: Class 1 (life expectancy more than 25 years).
  • Lyctine susceptibility: sapwood is not susceptible to lyctine borer attack.
  • Termite resistance: resistant.
  • Preservation: sapwood moderately resists treatment with preservatives.
  • Seasoning: slow seasoning timber with very low shrinkage and dries with minimal degrade.
  • Hardness: hard (rated 1 on a 6-class scale) to indent and work with hand tools.
  • Machining: works well for a high-density timber except for the presence of resin; a cutting angle of 20° recommended on interlocked, quarter-sawn material to prevent 'picking-up'.
  • Fixing: pre-drill before nailing.
  • Gluing: due to high density, machine and prepare surface immediately before gluing.
  • Finishing: be careful due to the resin; obtains a good finish.

Identification features

General characteristics

  • Sapwood: well defined from heartwood.
  • Heartwood: dark tan brown, lustrous planed surface, sometimes with subdued strip figure (pattern).
  • Texture: moderately fine and even, interlocked grain, hard to cut across the grain.

Wood structure

  • Vessels: medium size, mainly solitary, others in radial pairs or short multiples, evenly distributed; filled with tyloses.
  • Parenchyma (soft tissue): numerous, short, fine apotracheal strands and closely spaced tangential lines, often not clearly visible with hand lens.
  • Rays: moderately fine, not easily seen on a radial surface.
  • Ripple marks: characteristic and very distinct.
  • Intercellular canals: vertical canals, smaller than vessels, filled with white resin, concentric and often discontinuous.

Other features

  • Burning splinter test: match-size splinter burns to ash.

Research and resources

  • 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.