Tualang


INTRODUCTION

The Standard Malaysian Name for the timber of Koompassia excelsa (Leguminosae). Vernacular names applied include kayu raja (Sarawak), mengaris (Sabah) and tapang (Sarawak). This is a monospecific timber. The sapwood is buff-coloured or yellow-brown, often with a pink tinge and is sharply differentiated from the heartwood, which is reddish brown to deep brick-red-brown when fresh and darkens with age to a deep chocolate-brown.  

Also known as Mengaris (Brunei); Bengaris, Mengaris, Menggeris, Sialang, Tualang and Wehis (Indonesia); Koompassia (Papua New Guinea); Ginoo and Manggis (Philippines); and Tulae and Yuan (Thailand).


DENSITY

The timber is a Medium Hardwood with a density of 800-865 kg/m3 air dry.


NATURAL DURABILITY

Tualang is classified as moderately durable under exposed conditions. The durability rating is based on the standard graveyard tests conducted at the Forest Research Institute Malaysia (FRIM) on specimens of dimension 50 mm x 50 mm x 600 mm. In the first series of such tests, all 6 specimens were completely destroyed after 3.5 years (Foxworthy & Woolley, 1930). In the second test, 60 specimens were used and the average service life was 3 years (Jackson, 1965). The sapwood of the timber is susceptible to both powder-post beetle and fungi attacks, while the heartwood is readily destroyed by termites.


PRESERVATIVE TREATMENT

The timber is amenable to preservative treatment and is classified as easy to treat.


TEXTURE

Texture is rather coarse but even except in areas where included phloem occurs. Grain is interlocked, often deeply interlocked. 


STRENGTH PROPERTIES

The timber falls into Strength Group A (Engku, 1988b) or SG 3 (MS 544:Part 2:2001).


Strength Properties of Tualang 

Test Condition

Modulus of Elasticity(MPa)

Modulus of Rupture (MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear strength (MPa)

Green

16,400

102.0

53.4

7.17

11.3

Air dry

17,800

121.0

62.0

8.00

16.3


MACHINING PROPERTIES

It is easy to resaw and cross-cut when green but is slightly difficult to resaw when dry. Planing is easy in either condition and the surface produced is smooth to moderately smooth.


Machining Properties of Tualang

Test Condition

Sawing

Planing

Boring

Turning

Re-sawing

Cross Cutting

Ease of planing

Quality of finish

Ease of boring

Quality of finish

Ease of turning

Quality of finish

Green

easy

easy

easy

smooth

easy

rough

-

-

Air dry

slightly difficult

easy

easy

moderately smooth

slight difficult

rough

easy

moderately smooth


NAILING PROPERTY

Nailing property is rated as good.  


AIR DRYING

The timber dries moderately slowly to slowly with slight end-checking, surface-checking and insect attacks as the main sources of degrade. 13 mm thick boards take 3.5 months to air dry, while 38 mm thick boards take 6 months.


KILN-DRYING

Kiln Schedule E is recommended.


Kiln Schedule E 

Moisture Content (%)

Temperature (Dry-bulb)

Temperature (Wet-bulb)

Relative Humidity (%) (approx.)

F

C

F

C

Green

120

48.5

115

46.0

85

60

120

48.5

113

45.0

80

40

125

51.5

116

46.5

75

30

130

54.5

117

47.0

65

25

140

60.0

120

49.0

55

20

155

68.0

127

53.0

45

15

170

76.5

136

58.0

40


SHRINKAGE

Shrinkage is average, with radial shrinkage averaging 1.5% and tangential shrinkage averaging 1.7%.


DEFECTS

The major defect that is associated with the timber of tualang is the presence of hard abnormal tissues commonly known as included phloem. It is observed that tualang is even more severely riddled with included phloem than kempas (Koompassia malaccensis). In sawn timber, bands and patches of included phloem similar to those found in kempas can often be seen (Ser, 1981). These zones of abnormal tissues are likely to result in seasoning degrade and mechanical weakness in the timber. Some minor defects that have been recorded are shot holes, pin holes, heart rot and hollow pith. Apart from these, the logs of freshly-felled K. excelsa are generally free from other defects.


USES

When treated, the timber is suitable for all heavy construction, like posts, beams, joists, columns (heavy duty), piling, railway sleepers and power transmission poles. Untreated, the timber is suitable for flooring (heavy traffic), panelling, mouldings, heavy duty furniture, fender supports, office and shop fittings, tool handles (impact) and plywood.


REFERENCES

  1. Engku, Abdul Rahman Chik. 1988b. Basic And Grade Stresses For Some Malaysian Timbers. Malaysian Forest Service Trade Leaflet No. 38. The Malaysian Timber Industry Board And Forest Research Institute Malaysia, Kuala Lumpur. 13 pp.
  2. Foxworthy, F. W. & Woolley, H. W. 1930. Durability of Malayan Timbers. Malayan Forest Record No. 8.
  3. Jackson, W. F. 1965. The Durability of Malayan Timbers. Malayan Forest Service Trade Leaflet No. 28.
  4. Menon, P. K. B. 1986. Uses of Some Malaysian Timbers. Revised by Lim, S. C. Timber Trade Leaflet No. 31. The Malaysian Timber Industry Board and Forest Research Insitute Malaysia, Kuala Lumpur. 48 pp.
  5. MS 544: Part 2: 2001: Code Of Practice For Structural Use Of Timber. PermissibleStress Design of Solid Timber.
  6. Ser, C. S. 1981. Malaysian Timbers Kempas. Malaysian Forest ServiceTrade Leaflet No. 44.
  7. Ser, C. S. 1984. Malaysian Timbers - Tualang. Malaysian Forest Service Trade Leaflet No. 83. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 6 pp.
  8. Wong, T. M. 1982. A Dictionary of Malaysian Timbers. Revised by Lim, S.,C. & Chung, R. C. K. Malayan Forest Record No. 30. Forest Research Institute Malaysia Kuala Lumpur. 201 pp.