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Chengal


INTRODUCTION

The Standard Malaysian Name for the timber of Neobalanocarpus heimii (Dipterocarpaceae). Vernacular names applied include penak (Peninsular Malaysia). The name chengal is so popular, that many other species have been given vernacular names bearing the name chengal. Neobalanocarpus is a monotypic genus. The sapwood is light yellow and sharply defined from the heartwood, which is light yellow-brown with a distinct green tinge, darkening on exposure to dark purple-brown or rust-red.

Also known as Chengal (Brunei); and Chan Ta Khien, Chi-ngamat, Takian Chan and Takian Chantamaeo (Thailand).


DENSITY

The timber is a Heavy Hardwood with a density of 915-980 kg/m3 air dry.


NATURAL DURABILITY

The timber is classified as naturally durable and is normally very resistant to termite attack and fungal infestation. Under graveyard test conditions, untreated specimens of size 50 mm x 50 mm x 600 mm lasted 9 years. Treated specimen of the same size and test conditions lasted about 19 years. Untreated railway sleepers of size 238 mm x 125 mm x 1,950 mm laid under severe environmental conditions gave an average service life of 19 years.


PRESERVATIVE TREATMENT

This timber has been classified as moderately difficult to treat.


TEXTURE

Texture is fine and even, with shallowly to deeply interlocked grain.


STRENGTH PROPERTIES

The timber falls into Strength Group A (Engku, 1988b) or SG 1 (MS 544:Part 2:2001).


Strength Properties of Chengal

Test Condition

Modulus of Elasticity (MPa)

Modulus of Rupture  (MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear Strength (MPa)

Green

18,100

122

69

12

14

Air dry

19,600

149

75

12

14


MACHINING PROPERTIES

It is slightly difficult to resaw and is easy to moderately easy to cross-cut. Planing is easy and the planed surface produced is smooth.


Machining Properties of Chengal

Condition

Sawing

Planing

Boring

Turning

Rip-sawing

Cross-cutting

Ease of planing

Quality of finish

Ease of boring

Quality of finish

Ease of turning

Quality of finish

Green

slightly difficult

easy

easy

smooth

easy

smooth

-

-

Air dry

slightly difficult

moderately easy

easy

smooth

easy

smooth

easy

smooth


NAILING PROPERTY

Nailing property is rated as very poor.


AIR DRYING

The timber seasons slowly with moderate end-checking and surface-checking as the main sources of degrade. 13 mm thick boards take approximately 5 months to air dry, while 38 mm thick boards take 6 months.


KILN-DRYING

Kiln Schedule B is recommended. The timber dries very slowly and is extremely prone to surface-checking. 25 mm thick boards take approximately 30 days to kiln-dry from 50% to 10% moisture content.


Kiln Schedule B 

Moisture Content (%)

Temperature
(Dry Bulb)

Temperature
(Wet Bulb)

Relative Humidity (%) (approx.)

F

C

F

C

Green

105

40.5

101

38.0

85

40

105

40.5

99

37.0

80

30

110

43.5

102

39.0

75

25

115

46.0

105

40.5

70

20

130

54.5

115

46.0

60

15

140

80.0

118

47.5

50


SHRINKAGE

Shrinkage is fairly low, with radial shrinkage averaging 1.1% and tangential shrinkage averaging 2.6%.


DEFECTS

Small pin-holes, caused by ambrosia beetles boring into the living trees, are a common and characteristic defect of chengal. These small holes are often numerous, but although unsightly, they are only in exceptional cases sufficiently numerous to impair the strength of the timber. These ambrosia beetles die when the timber is seasoned and thus the damage is restricted almost entirely to that which occurs in the green timber. Big trees of chengal are sometimes hollow at the centre and badly attacked by large borers, and occasional trees are seriously infected by a fungus (Fomes spp.), which initially gains entry through broken branches or other wounds and eventually reduces the timber to a dark pulpy condition. With the exception of pin holes, the timber of chengal is free from knots and other defects characteristic of sawn timber.


USES

The timber is suitable for all forms of heavy construction, railway sleepers, heavy duty furniture, laboratory benches, bridges, marine construction, boat building, telegraphic and power transmission posts and cross arms, piling, mallets, flooring (heavy traffic), decking, vehicle bodies (framework and floor boards), fender supports, cooling towers (structural members), staircase (balusters, carriages, handrails, newels, risers, stringers, treads, bullnoses, round ends and winders), columns (heavy duty), door and window frames and sills, tool handles (impact), carving works and other uses where strength and durability are required.


REFERENCES

  1. Engku Abdul Rahman Chik. 1988b. Basic and Grade Stresses for Strength Groups of Malaysian Timbers. Malayan Forest Service Trade Leaflet No. 38. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 13 pp.
  2. Lopez, D.T. 1983. Malaysian Timbers - Chengal. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 7 pp.
  3. MS 544:Part 2:2001. Code of Practice for the Structural Use of Timber: Permissible Stress Design of Solid TImber.
  4. Wong, T.M. 1982. A Dictionary of Malaysian Timbers. Revised by Lim, S.C. & Chung R.C.K. Malayan Forest Records No. 30. Forest Research Institute Malaysia, Kuala Lumpur. 201 pp.

 

   
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