KERUING
INTRODUCTION
The Standard Malaysian Name for the timber of Dipterocarpus spp. (Dipterocarpaceae). Vernacular names applied include keruing (Peninsular Malaysia, Sabah and Sarawak) with various epithets, as well as other localised names which are too numerous to list here. The most commonly met species include D. elongatus, D. baudii, D. chartaceus, D. confertus, D. concavus, D. cornutus, D. costatus, D. crinitus, D. dyeri, D. gracilis, D. grandiflorus, D. kerrii, D. kunstleri, D. lowii, D. obtusifolius, D. rotundifolius, D. sublamellatus and D. verrucosus. The sapwood is lighter in colour than the heartwood and is invariably with a tinge of grey. The heartwood is red-brown to purple-red and darkens on exposure. The surface of the timber may be rather resinous and sticky when handled. Keruings that are believed to give the best yield of oleo-resin are D. cornutus, D. crinitus, D. grandiflorus, D. hasseltii and D. kerrii. In Thailand, D. alatus is the best known producer of this product.
Also known as Keruing (Brunei); Khlong and Thbaeng (Cambodia); Gurjan (India); Keruing, Kerup, Lagan and Tempudau (Indonesia); Mai nyang, Mai kung, Mai sat, Muak and Nha:ng (Laos); Eng, In, Kanyin and Kayin (Myanmar); Apitong and Panau (Philippines); Hora (Sri Lanka); and Heng, Hiang , Hieng, Plung, Yang, Yang-khon, Yang-na and Yang-pai (Thailand).
DENSITY
It is a Medium Hardwood with a density of 690-945 kg/m3 air dry in Peninsular Malaysia, and with a density of 595-865 kg/m3 air dry for the species found in Sabah.
NATURAL DURABILITY
The timber (depending on the species) is moderately durable to non-durable under exposed conditions in the tropics.
PRESERVATIVE TREATMENT
It is very easily treated with preservatives.
TEXTURE
Texture is moderately coarse to coarse but even, with straight to deeply interlocked grain.
STRENGTH PROPERTIES
Texture is moderately coarse to coarse but even, with straight to deeply interlocked grain.
MACHINING PROPERTIES
The timber of some species is easy to work, while that of others is moderately easy and some species are classified as slightly difficult. Planing is easy to slightly difficult and the finish is generally smooth.
AIR DRYING
The timber generally seasons well with some end-splitting and surface-checking as the main defects. The seasoning properties of some Dipterocarpus species tested are summarised below:
| Species | Time to air dry (months) | Remarks | |
|---|---|---|---|
| 13 mm thick boards | 38 mm thick boards | ||
| D. baudii | 3 | 5 | Fairly slow drying; moderate end-checking; slight cupping, bowing and spring. |
| D. cornutus | 4.5 | 6.5 | Slow drying; moderate end-checking; slight cupping, bowing and spring. |
| D. costulatus | 2 | 4 | Fairly fast drying; slight surface-checking; slight insect attack. |
| D. crinitus | 2 | 4 | Fairly fast drying; slight cupping, bowing. |
| D. grandiflorus | 3.5 | 5.5 | Fairly slow drying; moderate end-checking and cupping; slight bowing, spring and insect attack. |
| D. kerrii | 3 | 4 | Fairly slow drying; severe cupping, slight bowing, spring and checks. |
| D. kunstleri | 4 | 5.5 | Fairly slow drying; moderate end-checking; slight cupping, bowing and spring. |
| D. lowii | 3 | 5 | Fairly slow drying; slight cupping, bowing and spring. |
| D. sublamellatus | 3 | 5 | Fairly slow drying; moderate cupping, bowing; slight spring. |
| D. verrucosus | 3 | 5 | Fairly slow drying; moderate cupping, bowing and spring; slight end-checks, splitting and surface-checking. |
KILN-DRYING
Kiln Schedule D is recommended for kiln-drying. Care must be taken as this timber is prone to end-splitting and surface-checking.
| Kiln Schedule D | |||||
|---|---|---|---|---|---|
| Moisture Content (%) | Temperature (Dry Bulb) | Temperature (Wet Bulb) | Relative Humidity (%) (approx.) | ||
| °F | °C | °F | °C | ||
| Green | 105 | 40.5 | 101 | 38.0 | 85 |
| 60 | 105 | 40.5 | 99 | 37.0 | 80 |
| 40 | 105 | 40.5 | 96 | 35.5 | 70 |
| 35 | 110 | 43.5 | 97 | 36.0 | 60 |
| 30 | 115 | 46.0 | 97 | 36.0 | 50 |
| 25 | 125 | 51.5 | 101 | 38.0 | 40 |
| 20 | 140 | 60.0 | 105 | 40.5 | 30 |
| 15 | 150 | 65.5 | 112 | 44.5 | 30 |
SHRINKAGE
The shrinkage of the timber is summarised below:
| Species | Shrinkage (%) (Green to air dry) | Remarks | |
|---|---|---|---|
| Radial | Tangential | ||
| D. baudii | 2.3 | 5.6 | Very high shrinkage |
| D. cornutus | 3.1 | 5.1 | Very high shrinkage |
| D. costulatus | 2.9 | 3.3 | High shrinkage |
| D. crinitus | 2.1 | 3.5 | High shrinkage |
| D. grandiflorus | 1.6 | 4 | High shrinkage |
| D. kerrii | 2.6 | 6.6 | Very high shrinkage |
| D. kunstleri | 2.6 | 5.4 | Very high shrinkage |
| D. lowii | 2.7 | 4.5 | Very high shrinkage |
| D. sublamellatus | 2 | 5.5 | Very high shrinkage |
| D. verrucosus | 3.1 | 7.4 | Very high shrinkage |
MOVEMENT IN SERVICE
The movement of seasoned timber is classified under Type IV for D. sublamellatus (keruing kerut) and D. cornutus (keruing gombang) and Type V movement for D. kerrii (keruing gondol), D. costulatus (keruing kipas), D. grandiflorus (keruing belimbing) and D. lowii (keruing sol).
USES
This timber is suitable for heavy construction, posts, beams, joists, rafters, ship and boat building (keels, keelsons and framework), vehicle bodies (framework, floor boards and planking), container flooring and when treated, suitable for railway sleepers, harbour works, bridges, power-line poles and telegraph poles.
REFERENCES
- 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.
- 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 Ma