Kempas

Kempas

INTRODUCTION

The Standard Malaysian Name for the timber of Koompassia malaccensis(Leguminosae). Vernacular names applied include impas (Sabah) and menggris(Sarawak). This is a monospecific timber. The sapwood is white or pale yellow and is sharply defined from the heartwood, which is pinkish when fresh and darkens to bright orange-red or deep brown.

DENSITY

The timber is a Medium Hardwood with a density of 770-1,120 kg/m³ air dry. It was reported that the material from Sabah and Sarawak is much denser than the material from Peninsular Malaysia.

NATURAL DURABILITY

Based on the standard graveyard test of untreated specimens of dimension 51 mm x 51 mm x 610 mm, the wood is classified as moderately durable under the Malaysian condition. In a test conducted at the Forest Research Institute Malaysia (FRIM), the average service life for 161 untreated specimens was 2.5 years. The sapwood is very susceptible to both powder-post beetles and fungi attacks, while the heartwood is readily destroyed by termites. Kempas treated with the appropriate wood preservatives is very durable even under exposed condition. In an experiment, 40 test sticks (64 mm x 64 mm x 760 mm) with an average absorption of 224 kg/m³ (14 lb/ft³) of creosote were buried for the durability test. 25% of the specimens were destroyed after 35 years.

PRESERVATIVE TREATMENT

The timber is amenable to preservative treatment and it is classified as easy to treat.

TEXTURE

Texture is rather coarse but even except in areas where included phloem occurs. Grain is interlocked, often very interlocked.

STRENGTH PROPERTIES

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

Strength Properties of Kempas

Test Condition	Modulus of Elasticity(MPa)	Modulus of Rupture(MPa)	Compression parallel to grain (MPa)	Compression perpendicular to grain (MPa)	Shear strength(MPa)
Green	16,600	100	55	6	10
Air dry	18,600	122	66	8	12

MACHINING PROPERTIES

It is slightly difficult to resaw and easy to cross-cut when green but is difficult to resaw and slightly difficult to cross-cut when dried. Planing is easy in both conditions and the quality of the surfaces ranges from smooth to rough.

Machining Properties of Kempas 

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	slightly difficult	easy	easy	smooth to rough	easy	rough to slightly ragged	-	-
Air dry	difficult	slightly difficult	easy	smooth	slightly difficult	rough	slightly difficult	rough

NAILING PROPERTY

Nailing property is rated as poor.

AIR DRYING

The timber seasons fairly slowly with very few defects except for insect attacks in the sapwood. 13 mm thick boards take approximately 2 months to air dry, while 38 mm thick boards take 4 to 6 months.

KILN-DRYING

Kiln Schedule E is recommended. 25 mm thick boards take approximately 8 days to kiln-dry. Degrade is mainly in the form of spring although surface-checking and end-splitting may occur in thicker specimens. Splitting can be severe in areas where included phloem occurs.

Kiln Schedule E

Moisture Content (%)	Temperature (Dry Bulb)		Temperature (Wet Bulb)		Relative Humidity (%) (approx.)
	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 on the high side with radial shrinkage averaging 2% and tangential shrinkage averaging 3%.

DEFECTS

Though some borer damage have been recorded, the logs of freshly felled K. malaccensis are generally free from defects. The major defect that is associated with the timber of kempas is the presence of included phloem. Rings of included phloem often show up conspicuously at the cross-section of the log. In sawn timber, bands of included phloem extending longitudinally can often be seen on the radial surfaces. Patches of included phloem can also be seen on sawn timbers. These zones of abnormal tissue are hard and usually give rise to seasoning degrade and mechanical weakness in the timber.   

USES

The timber when treated with preservatives is suitable for all heavy constructional works, posts, beams, joists, rafters, piling, columns (heavy duty), fender supports, pallets (permanent and heavy duty), door and window frames and sills, tool handles (impact), bridges, wharves, marine construction, railway sleepers, telegraphic and power transmission posts and cross arms. When untreated, the timber is suitable for structures under cover, flooring, panelling, mouldings, vehicle bodies (framework and floor boards), plywood and charcoal manufacture.