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 |
Temperature |
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
-
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.
-
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.
-
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.
-
MS 544:Part 2:2001. Code of practice for the Structural Use of Timber: Permissible Stress Design of Solid Timber.
-
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.
