Rengas


INTRODUCTION

The Standard Malaysian Name for the timber of Gluta spp. and Melanochyla spp. (Anacardiaceae). Vernacular names applied are usually rengas (Peninsular Malaysia, Sabah and Sarawak) with various epithets. The major species contributing to the timber include Gluta aptera, G. elegans, G. malayana, G. renghas, G. torquata, G. wallichii, G. wrayi; Melanochyla auriculata, M. bracteata, M. caesia and M. fulvinervis. The sapwood is light pink-brown or light brown and is sharply differentiated from the heartwood, which is dark red-brown or deep blood-red, with bands of darker, almost black streaks.

Also known as Rengas (Brunei); Kroeul (Cambodia); Gluta (India); Anga, Poei and Rengas (Indonesia); Mai nam kiang (Laos); Burma Gluta, Chay, Thayet-thitsi and Thitsi (Myanmar); Hekakoro (Papua New Guinea); Lingas (Philippines); and Rak and Rak-ban (Thailand).


DENSITY

The timber is a Medium Hardwood with a density of 640-960 kg/m3 air dry.


NATURAL DURABILITY

The timber is moderately durable, being susceptible to termite attacks.


PRESERVATIVE TREATMENT

The heartwood is extremely difficult to treat with preservatives, while the sapwood is amenable.


TEXTURE

Texture is moderately coarse to fairly fine and even, with interlocked or occasionally straight grain.


STRENGTH PROPERTIES

The timber falls into Strength Group B (Engku, 1988b) or SG4 (MS 544: Part 2: 2001).


Strength Properties of Rengas (G. torquata)

Test Condition

Modulus of Elasticity(MPa)

Modulus of Rupture(MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear Strength (MPa)

Green

14,000

81

41.4

5.31

10.6

Air dry

14,900

111

59.4

7.65

13.2


MACHINING PROPERTIES

It is slightly difficult to resaw and cross cut and the planed surface is only moderately smooth.


Machining Properties of Rengas (G. torquata)

Test 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

easy to slightly difficult

easy

easy

moderately smooth

slightly difficult

slightly rough

-

-

Air dry

slightly difficult

slightly difficult

difficult

moderately smooth

slightly difficult

slightly rough

slightly difficult

rough


NAILING PROPERTY

The nailing property is rated as excellent.


AIR DRYING

The timber seasons moderately slowly, with slight twisting and insect attacks as the main sources of degrade. 13 mm thick boards take approximately 2 months to air dry, while 38 mm thick boards take 5 months.


KILN-DRYING

Kiln Schedule E is recommended.


Kiln Schedule E

Moisture Content (%)

Temperature
(Dry Bulb)

Temperature (Wet Bulb)

Relative Humidity (%)

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 fairly low, radial shrinkage averages 1.0% while tangential shrinkage averages 1.8%.


DEFECTS

The logs of rengas are generally free from defects except for few heart shakes.


USES

Due to the poisonous nature of the sap, the timber is not very often exploited. The seasoned timber, however, is quite safe to handle and is highly prized as a cabinet wood due to its streaky figure and blood-red colour. The timber is also suitable for decorative works, panelling, mouldings, superior joinery, picture frames, flooring, plywood, furniture, railway sleepers, posts, beams, joists, rafters, pallets (permanent light duty), door and window frames and sills (internal use), tool handles (impact), ornamental items and walking sticks. The timber is strong enough for medium construction provided it is protected from termites.


REFERENCES

  1. Engku, Abdul Rahman Chik. 1988b. Basic And Grade Stresses For Some 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. 1984. Malaysian Timbers - Rengas. Malaysian Forest Service Trade Leaflet No. 87. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 8 pp.
  3. 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.
  4. MS 544: Part 2: 2001: Code Of Practice For Structural Use Of Timber. Permissible Stress Design of Solid Timber.
  5. 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.