Resak


INTRODUCTION

The Standard Malaysian Name for the tree and timber of Cotylelobium spp. and Vatica spp. (Dipterocarpaceae). Vernacular names applied include resak (Peninsular Malaysia, Sabah and Sarawak) with various epithets, balau (Peninsular Malaysia) in error, damar keluang (Pahang), jenuong (Johor) and keruing babi (Peninsular Malaysia). Major species include Cotylelobium lanceolatum, C. melanoxylon; Vatica bella, V. cuspidata, V. flavida, V. havilandii, V. heteroptera, V. lowii, V. maingayi, V. mangachapoi, V. nitens and V. scortechinii. The sapwood is lighter in colour than the heartwood and is sharply defined in Cotylelobium but not generally so in Vatica. The heartwood is pale yellow when fresh and turns to deep red-brown on exposure in Cotylelobium and a fine brown with a green tinge in Vatica.

Also known as Resak (Brunei); Chrama:hs (Cambodia); Vatica (India); Giam, Resak and Resak bukit (Indonesia); Chik dong, Mai ka cha, Mai si and Mai si khao (Laos); Vatica (Papua New Guinea); Narig (Philippines); and Chan Thip, Dam Darng, Khian, Khiem, Kiam, Pan-Cham, See, Tamsao and Yang-nu (Thailand).

  
DENSITY

The timber is a Heavy Hardwood with a density of 655-1,155 kg/m3 air dry. 


NATURAL DURABILITY

Graveyard tests on V. cuspidata, a species with an average air dry density of 1,040 kg/m3 indicated that the timber has an average service life of 14 years under natural conditions. The timber is therefore, classified as very durable under Malaysian conditions (Jackson, 1965). Desch (1941) recorded that tests carried out to determine the quality of resak timber indicated that some forms of resak were found to be exceptionally durable (presumably the heavier varieties), ranking with the best forms of balau and giam, and the inferior forms (presumably the lighter varieties) would appear to be at least moderately durable. Burkill (1935) stated that the timber of Cotylelobium is of excellent quality and resistant to Teredo, a type of marine borer. Burgess (1966) however, reported that the timber of Vatica species is not resistant to marine borers and failed within 12 months in Papua New Guinea. In general, resak should not be accepted as resistant to marine borers, but material of Cotylelobium, since it contains silica, is likely to be more resistant than Vatica.


PRESERVATIVE TREATMENT

Generally, preservative treatment is not necessary for Malaysian Heavy Hardwoods including the timber of resak. The timber was quoted as very difficult to treat (Lee and Chu, 1974). In general, the heartwood of the hard and heavy forms of resak are expected to be as difficult to treat as other Malaysian Heavy Hardwoods, e.g. balau, chengal and bitis. It is therefore, unlikely that resak will absorb preservatives of any worthwhile quantity except possibly for the sapwood of the lighter species.


TEXTURE

Texture is fine and even, with straight or only shallowly interlocked grain.


STRENGTH PROPERTIES

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


Strength Properties of Resak

Species

Test Condition

Modulus of Elasticity(MPa)

Modulus of Rupture(MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear Strength (MPa)

V. cuspidata

Green

18,100

105

61

12

13

V. stapfiana

Green

14,400

81

42

5

9


MACHINING PROPERTIES

It is difficult to resaw and cross-cut in Vatica, while Cotylelobium is moderately easy to slightly difficult to resaw. Planing is easy to slightly difficult and the finished surface is smooth. 


Machining Properties of Resak

Species

Test condition

Sawing

Planing

Boring

Turning

Resawing

Cross- cutting

Ease of planing

Quality of finish

Ease of boring

Quality of finish

Ease of turning

Quality of finish

C. malayanum

Green

moderately easy

moderately easy

easy

smooth

easy

smooth

-

-

Air dry

slightly difficult

moderately easy

easy

smooth

easy

smooth

slightly difficult

moderately smooth

V. cuspidata

Green

difficult

difficult

slightly difficult

smooth

easy

smooth

-

-

Air dry

difficult

difficult

slightly difficult

smooth

easy

smooth

slightly difficult

moderately smooth

V. stapfiana

Green

difficult

difficult

slightly difficult

smooth

easy

smooth

-

-

Air dry

difficult

difficult

slightly difficult

smooth

easy

smooth

-

-


AIR DRYING

The timber seasons fairly slowly with very negligible degrade. Only slight cupping, end-checking, splitting and surface-checking are noted during drying. 13 mm thick boards take approximately 3 months to air dry, while 38 mm thick boards take 5 months.


KILN-DRYING

Kiln Schedule B is recommended. Resak, which is hard and heavy as chengal (Neobalanocarpus heimii), needs very slow drying as it is extremely prone to surface-checking. In order to minimise the drying costs and defects, the timber should be air dried to below 30% moisture content before kiln-drying.


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 high, especially in the tangential direction. Radial shrinkage averages 1.5% while tangential shrinkage averages 3.4%.


DEFECTS

The timber is generally free from any major defects except in some logs, which may contain some heart shakes and some accompanying decay. Compression failure is occasionally present in some logs. No ‘pin’ or ‘shot’ hole borer attack in the heartwood has been observed but the sapwood is liable to powder-post beetle attacks. Surface-checking of the timber is common but not severe. Some resin pockets may be present.


USES

The timber is suitable for all forms of heavy construction, bridges, piling, marine construction, beams, posts, joists, pallets (permanent heavy duty), door and window frames and sills, tool handles (impact), flooring (heavy traffic), power transmission poles, laboratory benches, vehicle bodies (framework and floor boards), railway sleepers, fender supports, staircase (angle blocks, rough brackets, carriage, riser, stringer, tread, bullnose, round end and winder), cooling tower (structural members), telegraphic and power transmission posts and cross arms, heavy duty furniture and wooden containers.


REFERENCES

  1. Burgess, P. F. 1966. Timbers of Sabah. Sabah Forest Record No.6.
  2. Burkill, I. H. 1935. A Dictionary of the Economic Products of the Malay Peninsula. Crown Agents for the Colonies, London.
  3. Desch, H. E. 1941. Manual of Malayan Timbers.Vol.1. Malayan Forest Record No.15.
  4. Engku, Abdul Rahman Chik. 1988b. Basic And Grade Stresses For Some Malaysian Timbers. Timber Trade Leaflet No. 38. The Malaysian Timber Industry Board And Forest Research Institute Malaysia, Kuala Lumpur. 13 pp
  5. Jackson, W. F. 1965. Durability of Malayan Timbers. Malayan Forest Service Trade Leaflet No.38.
  6. Lee, Y. H. & Chu, Y. P. 1974. Commercial Timbers of Peninsular Malaysia. Malaysian Timber Industries Board.
  7. Lim, S.C. 1982. Malaysian Timbers - Resak. Malaysian Forest Service Trade Leaflet No. 62. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 9 pp.
  8. 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.
  9. MS 544: Part 2: 2001: Code Of Practice For Structural Use Of Timber. Permissible Stress Design of Solid Timber.
  10. 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.