Merawan

INTRODUCTION

The Standard Malaysian Name for the light timbers of Hopea spp. (Dipterocarpaceae). Vernacular names applied are usually merawan (Peninsular Malaysia) with various qualifying epithets, luis (Sarawak), mang (Sarawak) and selangan (Sabah and Sarawak) with various epithets. Gagil is used for H. sangal in Sabah. The timber is usually mixed with the lighter species of Shorea and sold as selangan batu No. 2 in Sabah. Major species of merawan include H. beccariana, H. dryobalanoides, H. dyeir, H. ferruginea, H. glaucescens, H. griffithii, H. latifolia, H. mengarawan, H. montana, H. myrtifolia, H. nervosa, H. odorata, H. pierrei, H. pubescens, H. sangal, H. sublanceolata and H. sulcata. The sapwood is generally lighter in colour and poorly defined from the heartwood, which is yellow when fresh but darkens to light brown or red-brown on exposure.

Also known as Merawan (Brunei); Koki khsach, Koki:r, Popel and Popel mosau (Cambodia); Hopea and Thingan (India); Dammar mata kuching, Gagil and Merawan (Indonesia); Khe:n and Mai khaen heua (Laos); Thingan (Myanmar); Light hopea (Papua New Guinea); Manggachapui (Philippines); Chan-phu, Takhian-Tong, Takian and Takian–Thong (Thailand); and Kien-kien and Sao den (Vietnam).


DENSITY

The timber is a Medium Hardwood with a density of 495-980 kg/m3 air dry.


NATURAL DURABILITY

The timber is moderately durable under exposed conditions. It is especially resistant to fungal infection under normal conditions. The sapwood is susceptible to heavy damage by termites and in damp situations by fungus (Thomas, 1970).


PRESERVATIVE TREATMENT

The timber is difficult to treat with preservatives.


TEXTURE

Texture is moderately fine and even, with interlocked grain.


STRENGTH PROPERTIES

The timber falls into Strength Group B (Engku, 1988b) or SG 4 (MS 544:Part 2:2001).


Strength Properties of Merawan
 

Species

Moisture Content(%)

Modulus of Rupture(MPa)

Modulus of Elasticity(MPa)

Impact bending (mm)

Compression parallel to grain (MPa)

Shear parallel to grain (MPa)

H. nervosa

64

92

15,500

760

50.8

9.3

H. sulcata

61

90

15,000

690

45.9

9.0


MACHINING PROPERTIES

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


Machining Properties of Merawan 
 

Species

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

H. nervosa

Green

easy

easy

easy

smooth

slightly difficult

smooth

-

-

Air dry

moderately easy

moderately easy

fairly easy

smooth

slightly difficult

moderately smooth

easy

smooth

H. sulcata

Green

easy

easy

easy

smooth

easy

smooth

-

-

Air dry

easy

easy

easy

smooth

easy

smooth

easy

smooth


NAILING PROPERTY

Nailing property is rated as very poor.


AIR DRYING

The timber seasons slowly with slight cupping as the only defect. 13 mm thick boards take approximately 4 months to air dry while 38 mm thick boards take 6 months.


KILN-DRYING

Kiln Schedule H is recommended. 25 mm thick boards take approximately 5 days to kiln-dry from 50 to 10% moisture content. There is no record of drying degrade.


Kiln Schedule H

Moisture Content (%)

Temperature (Dry Bulb)

Temperature (Wet Bulb)

Relative Humidity (%) (approx.)

° F

° C

° F

° C

Green

135

57.0

127

53

80

50

135

57.0

126

52

75

40

140

60.0

126

52

65

30

150

65.5

129

54

55

20

170

76.5

136

58

40


SHRINKAGE

Shrinkage is average, with radial shrinkage of H. sulcata averaging 0.9% and tangential shrinkage averaging 2.2%.


DEFECTS

Hollow and spongy heart are the common defects found in many merawan logs although they are not nearly as extensive as in most red merantis. Compression failures are found in the areas with spongy heart (Thomas, 1970). The timber of some species (H. sulcata, H. myrtifolia, H. dyeri and H. mengarawan) has been found to be very susceptible to damage by ambrosia beetles, whereas the timber of other species appears to be resistant (Desch, 1941). Most species of merawan are immune to powder-post beetle attacks, while other species are moderately susceptible (Menon, 1957). The sapwood of all species is liable to sapstain infection.   


USES

The timber is suitable for rafters, joists, door and window frames and sills (internal use), panelling, mouldings, partitioning, joinery, furniture, plywood, flooring, decking, staircase (angle blocks, rough bracket, baluster, balustrade, carriage, newel, riser, sprandrel framing, stringer, tread, bullnose, round end and winder), columns (light duty), railway sleepers, vehicle bodies (framework, floor boards and planking), ship and boat building (keels, keelsons, framework and general planking), cooling tower (structural members) and tool handles (non impact). The heavier species are suitable for heavy construction under cover.


REFERENCES

  1. Desch, H. E. 1941. Dipterocarp Timber of the Malay Peninsula. Mal. For. Rec. No. 14.
  2. Engku Abdul Rahman Chik. 1998b. 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.
  3. Ho, K. S. 1981. Malaysian Timbers - Merawan. Malaysian Forest Service Trade Leaflet No. 53. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 10 pp.
  4. Menon, K. D. 1957. Susceptibility of Commercial Species of Malayan Timbers to Powder-post Beetle Attack. Mal. For. Vol. 20 (1) p. 19-23.
  5. 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 Institute Malaysia, Kuala Lumpur. 48 pp.
  6. MS 544:Part 2:2001. Code of Practice for the Structural Use of Timber: Permissible Stress Design of Solid Timber.
  7. Thomas, A. V. 1970. Malayan Timbers - Sepetir - Merawan. Mal. For. Ser. Trade Leaflet No. 16. (Reprinted).
  8. 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.