Geronggang


INTRODUCTION

The Standard Malaysian Name for the lightweight timbers of Cratoxylum spp. (Guttiferae). Vernacular names applied include dat (Sarawak), di’it (Sarawak), kirap (Sarawak), labakan (Sarawak), manat (Sarawak), mertilan (Sarawak), pidang (Sarawak), serungan (Sabah), serungan labakan (Sarawak), tat (Sarawak) and timau (Sarawak). Major species include C. arborescens and C. glaucum. The sapwood is yellow with a pink tinge and is moderately sharply defined from the heartwood, which is dark pink or light brick-red.

Also known as Geronggang (Brunei); Adat, Gerunggung and Medang baro (Indonesia); Paguringon (Philippines); and Kalong-ngae and Ngong-ngang (Thailand).

DENSITY

The timber is a light hardwood with a density of 350-610 kg/m3 air dry.

NATURAL DURABILITY

From the graveyard test conducted on untreated specimens, geronggang is destroyed by termites within one year. It is therefore classified as non-durable.

PRESERVATIVE TREATMENT

Although the timber is not durable, it is easily treated with preservatives.

TEXTURE

Texture is moderately coarse but even, with straight or sometimes shallowly interlocked grain.

STRENGTH PROPERTIES

The timber falls into Strength Group D (Engku, 1988b) or SG 7 (MS 544:Part 2:2001).


Strength Properties of Geronggang (C. arborescens)

Test Condition

Modulus of Elasticity(MPa)

Modulus of Rupture(MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shear Strength(MPa)

Green

8,000

40

18.3

1.93

5.1


MACHINING PROPERTIES

The timber is easy to resaw and cross-cut. Planing is easy and the planed surface is smooth.


Machining Properties of Geronggang (C. arborescens)

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

easy

easy

easy

smooth

easy

rough

easy

rough


NAILING PROPERTY

Nailing property is rated as excellent.

AIR DRYING

The timber seasons rapidly without any form of degrade at all. 38 mm thick boards take approximately 2 months to air dry.

KILN-DRYING

Kiln Schedule E is recommended and the timber is reported to dry well under this schedule.
 

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 high, with radial shrinkage averaging 2.2% and tangential shrinkage averaging 4.2%.

USES

The timber is suitable for decorative works, joinery, furniture, cabinet making, counter tops, panelling, mouldings, interior finishing, ornamental items, clogs, plywood, particleboard, wood-wool cement-board, pencil manufacture and staircase (apron lining and handrail).

REFERENCES

  1. Ani Binti Sulaiman. 1987. Malaysian Timbers - Geronggang. Timber Trade Leaflet No. 104.The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 5 pp.
  2. 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.
  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 Institute Malaysia, Kuala Lumpur. 48 pp.
  4. MS 544:Part 2:2001. Code of practice for the 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 Records No. 30. Forest Research Institute Malaysia, Kuala Lumpur. 201 pp.
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