Kekabu

INTRODUCTION

The Standard Malaysian Name as well as the ASEAN Standard Name for the timber of Bombax spp. (Bombacaceae). Vernacular names applied include kekabu hutan (Peninsular Malaysia), kapok (Sabah) and tambaluang (Sabah). Major species include B. ceiba and B. valetonii. The sapwood is white and sharply differentiated from the heartwood, which is pale straw-coloured.

Also known as Didu and Semul (India); Randu alas (Indonesia); Ngui ban (Laos); Didu, Letpan and Thinbaw (Myanmar); Bombax and Kapok (Papua New Guinea); Malabulak (Philippines); Ngui (Thailand); and Pílang (Vietnam).


DENSITY

The timber is soft and light with a density of 415-545 kg/m3 air dry.


NATURAL DURABILITY

Based on the graveyard tests of untreated specimens under natural conditions conducted at the Forest Research Institute Malaysia (FRIM), the wood is classified as non-durable with an average service life of about 0.9 year (Mohd. Dahlan & Tam, 1985). When the timber was treated with creosote to an average absorption of 592 kg/m3 (37 lb/ft3) by the open-tank method and tested, it was found that there was no change after 12 years, indicating that treated kekabu could be rendered extremely durable.


PRESERVATIVE TREATMENT

The timber is extremely easy to treat with preservatives. 


TEXTURE

Texture is moderately coarse and even, with straight or slightly interlocked grain.


STRENGTH PROPERTIES

The timber falls into Strength Group D (Burgess, 1958). The strength properties of kekabu are shown in the table below.


Strength Properties of Kekabu (B. valetonii) 

Test Condition

Moisture Content (%)

Modulus of Rupture(MPa)

Modulus of Elasticity  (MPa)

Impact bending(mm)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Side hardness(Newton)

Shear parallel(MPa)

Green

132

24

4,800

180

14.1

1.03

980

3.3

Air dry

16.5

28

5,000

180

20.3

1.37

1,070

3.2


MACHINING PROPERTIES

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


Machining Properties of Kekabu (B. valetonii) 

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

moderately smooth

easy

moderately smooth

-

-

Air dry

easy

easy

easy

smooth

easy

moderately smooth

easy

moderately smooth


NAILING PROPERTY

Nailing property is excellent.


AIR DRYING

The timber seasons fairly rapidly with negligible degrade except for fungal and insect attacks. 13 mm thick boards take 2.5 months to air dry, while 38 mm thick boards take 3.5 months.


SHRINKAGE

Shrinkage is average with radial shrinkage averaging 1.7% while tangential shrinkage averaging 2.4%.


DEFECTS

Logs of two species of the Bombacaceae were examined and found to be remarkably sound. No sign of "Spongy heart" was encountered and the only defects observed were occasional longhorn beetle attack, the galleries being about 1.9 cm in diameter. The sapwood of all species appears to be relatively immune to infection from blue-stain fungi, although when fresh it contains abundant starch (Desch, 1941). The timber is very susceptible to powder-post beetle attacks (Wong, 1976).


USES

The timber is suitable for use as a low strength utility timber, packing boxes and crates and match boxes. However, the core material of the timber, which is reddish brown in colour, may be rather attractive and if it is properly processed, can be used for decorative furniture, panelling, mouldings, plywood, cigar boxes and other ornamental items.


REFERENCES

  1. Burgess, H. J. 1958. Strength Grouping of Malaysian Timbers. Malayan Forest Service Trade Leaflet No. 25. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 15 pp.
  2. Desch, H. E. 1941. Manual of Malayan Timbers. Vol.1. Mal. For. Rec. No. 15.
  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. Mohd. Dahlan Jantan and Tam, M. K. 1985. Unpublished report.
  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.
  6. Zainuddin Bin Mohd. Yunos. 1985. Malaysian Timbers - Kekabu. Timber Trade Leaflet No. 98. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 4 pp.