Jelutong

INTRODUCTION

The Standard Malaysian Name for the timber of Dyera spp. (Apocynaceae). Vernacular names applied include jelutong (Peninsular Malaysia, Sabah and Sarawak) with various epithets. Major species include D. costulata and D. polyphylla. The sapwood is not distinguished from the heartwood, which is creamy white to pale straw-coloured.

Also known as Jelutong (Brunei); Jelutung (Indonesia); and Jelutong, Teen-pet daeng and Yelutong (Thailand).


DENSITY

The timber is a Light Hardwood with a density of 420-500 kg/m3 air dry.


NATURAL DURABILITY

The timber of jelutong is classified as not durable under the exposed conditions. The durability rating is based on the standard graveyard tests of untreated D. costulata specimens of dimension 50 mm x 50 mm x 600 mm conducted at the Forest Research Institute Malaysia (FRIM). In the first series of such tests, all 68 specimens were completely destroyed within six months (Foxworthy & Wodley, 1930). In the second test, 40 specimens were used and the average service life was 1.4 years (Jackson, 1965). The timber is known to be very susceptible to both powder-post beetles and termite attacks. It is also very liable to blue stain in the green state.  


PRESERVATIVE TREATMENT

The timber is very amenable to preservative treatment.


TEXTURE

Texture is moderately fine and even, with almost straight grain.


STRENGTH PROPERTIES

The timber falls into Strength Group D (Engku, 1988b) or SG 6 (MS 544:Part 2:2001).


Strength Properties of Jelutong

 Test Condition

Modulus of Elasticity(MPa)

Modulus of Rupture(MPa)

Compression parallel to grain (MPa)

Compression perpendicular to grain (MPa)

Shearing 
strength(MPa)

Green

7,900

38.0

21.0

1.9

5.0

Air dry

8,100

50.0

27.0

2.7

6.0


MACHINING PROPERTIES

It is easy to saw and plane and produces a smooth surface despite its softness.


Sawing and Woodworking Properties of Jelutong

 Test Condition

Sawing

Planning

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

smooth

-

-

Air dry

easy

easy

easy

smooth

easy

smooth

easy

smooth


NAILING PROPERTY

Nailing property is excellent.


AIR DRYING

The timber seasons fairly rapidly without serious degrade, except for staining and powder-post beetle attacks but the common practice of dipping the timber in preservatives immediately after sawing has largely overcome this problem. 13 mm thick boards take 1.5 months to air dry, while 38 mm thick boards take 3 months.


KILN-DRYING

Kiln Schedule H is recommended.


Kiln Schedule H

Moisture Content (%)

Temperature
(Dry Bulb)

Temperature
(Wet Bulb)

Relative Humidity (%)

F

C

F

C

Green

135

57.0

127

53.0

80

50

135

57.0

126

52.0

75

40

140

60.0

126

52.0

65

30

150

65.5

129

54.0

55

20

170

76.5

136

58.0

40


SHRINKAGE

Shrinkage is fairly low, with radial shrinkage averaging 0.8% and tangential shrinkage averaging 2%.


MOVEMENT IN SERVICE

The movement of seasoned timber is classified under Type II.


DEFECTS

The logs are generally free from common defects. However, logs that have been damaged through bad and careless tapping are liable to fungal and insects infestation. Such attacks also occur in logs that have been left for some time in the forest after felling. Sap-stain fungi and ambrosia beetles are known to attack the logs (Desch, 1941). These attacks result in blue stains and tunnels in the log. Freshly sawn timbers are also prone to mould, blue stain and insect attacks. In some instances, the attack may occur few hours after sawing.


USES

Jelutong is the favourite timber for pencil manufacture. It is also suitable for plywood, packing boxes and crates, pattern making, carving works, disposable chopsticks, tooth picks, picture frames, drawing boards, black boards, battery separators, toys and wooden shoe heels.


REFERENCES

  1. Desch, H. C. 1941. Manual of Malayan Timbers. Mal. For. Rec. No. 15 Vol. 1.
  2. 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.
  3. Foxworthy, F. W. & Wodley, H. W. 1930. Durability of Malayan Timbers. Mal. For. Rec. No.8.
  4. Jackson, W. F. 1965. The Durability of Malayan Timbers. Mal. For. Ser. Trade Leaflet No.28.
  5. 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.
  6. MS 544:Part 2:2001. Code of Practice for the Structural Use of Timber: Permissible Stress Design of Solid Timber.
  7. Ser, C. S. 1981. Malaysian Timbers - Jelutong. Timber Trade Leaflet No. 55. The Malaysian Timber Industry Board and Forest Research Institute Malaysia, Kuala Lumpur. 6 pp.
  8. 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.