Neobalanocarpus

Neobalanocarpus
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Malvales
Family: Dipterocarpaceae
Genus: Neobalanocarpus
Species: N. heimii
Binomial name
Neobalanocarpus heimii
(King) P. Ashton

Neobalanocarpus is a monotypic genus of plants in the family Dipterocarpaceae. The single species, Neobalanocarpus heimii, is a tropical hardwood tree. Common names for the tree and its wood products include chengal, chan ta khien, chi-ngamat, takian chan, and takian chantamaeo. The tree grows over 60 m (197 ft) tall. Chengal is considered the number one wood (classified as heavy hardwood) of Malaysia and export of logs is prohibited due to its scarcity.

Distribution

Neobalanocarpus heimii is endemic to the Malay Peninsula and grows under quite a range of conditions of soils and topography in Peninsular Malaysia (and southern Thailand) from low flat sem-swamp to hills, but appears to thrive best on undulating land with light sandy soils. See Wildlife of Malaysia. [1]

Chengal tree, Peninsula Malaysia, 2005

Description

Sapwood is well defined. When freshly sawn, the heartwood is light yellow-brown with a distinct greenish tinge, darkening on exposure to dark purple-brown or rust red.

Grain is interlocked.

Texture is fine and even.

Vessels are with simple perforations and medium-sized, mostly solitary but with a few arranged radially in radial pairs and multiples of 2 to 4, evenly distributed without any clear arrangement and filled with tyloses.

Wood parenchyma is abundant, consisting of both apotracheal and paratracheal types. Apotracheal type consists of irregularly spaced bands of variable thickness and short closely spaced tangential lines extending from ray to ray. Paratracheal parenchyma is sparse, as incomplete narrow borders, not clearly visible with hand lens.

Rays are moderately fine to medium-sized, visible to the naked eye on the cross-section.

Ripple marks characteristic and very distinct.

Intercellular canals are vertical and typically smaller than the vessels, in concentric formations. [2]

Physical Properties

Property Value
Air-dry-density: 915 – 980 kg/m3
Shrinkage Radial: 1.1%
Shrinkage Tangential: 2.6%

[3]

Air-drying

The timber seasons slowly with moderate end-checking and surface-checking as the main sources of degrade. 13 mm thick boards take approximately 5 months to air dry, while 38 mm thick boards take 6 months. [4]

Kiln-drying (schedule)

Moisture Content (%) of the wettest timber on the air-inlet side at which changes are to be made Temperature (Dry bulb) Temperature (Wet bulb) Relative humidity (%) (approx)
Green 40.5 °C (105 °F) 38.0 °C (100 °F) 85
40 40.5 °C (105 °F) 37.0 °C (98.6 °F) 80
30 43.5 °C (110 °F) 37.0 °C (98.6 °F) 75
25 46 °C (115 °F) 37.0 °C (98.6 °F) 70
20 54.5 °C (130 °F) 37.0 °C (98.6 °F) 60
15 60 °C (140 °F) 37.0 °C (98.6 °F) 50

[5]

Mechanical Properties

Property Value
Strength group: greater than 55.2 MPa, extremely strong
Static bending MOE (Modulus of Elasticity): 19,600 MPa
Static bending MOR (Modulus of Rupture): 149 MPa
Compression Strength Perpendicular to grain: 12.00 MPa
Compression Strength Parallel to grain: 75.20 MPa
Shear strength: 13.90 MPa

[6]

Treatability

65 – 95 kg/m3absorption of preservative in open-tank treatment using a mixture of 50% creosote and 50% diesel oil heated to a temperature of 87 °C in 2 1/2 hours and maintained at this temperature for 1 hour before cooling to room temperature over a period of 16 hours. This ranks Chengal as "moderately difficult" to treat (3rd most difficult in treatability group ranking from extremely easy to very difficult).

Working Properties

Planing is known to be easy and a smooth finish is easily achieved

Boring is not hard

Turning is easy as well and a smooth finish is achieved

Nailing is very difficult and mostly a hole has to be predrilled to receive a nail

Defects

Small pin-holes, caused by ambrosia beetles boring into the living trees, are a common and characteristic defect of Chengal. These small holes are often numerous, but although unsightly, they are only in exceptional cases sufficiently numerous to impair the strength of the timber. These ambrosia beetles die when the timber is seasoned and thus the damage is restricted almost entirely to that which occurs in the green timber. Big trees of Chengal are sometimes hollow at the centre and badly attacked by large borers, and occasional trees are seriously infected by a fungus (Fomes spp.), which initially gains entry through broken branches or other wounds and eventually reduces the timber to a dark pulpy condition. With the exception of pin holes, the timber of chengal is free from knots and other defects characteristic of sawn timber. [7]

Durability

Chengal in a sawmill in Terengganu state, 2003

The timber is classified as naturally durable and is normally very resistant to termite attack and fungal infestation. Under graveyard test conditions, untreated specimens of size 50 mm x 50 mm x 600 mm lasted 9 years. Treated specimen of the same size and test conditions lasted about 19 years. Untreated railway sleepers of size 238 mm x 125 mm x 1,950 mm laid under severe environmental conditions gave an average service life of 19 years. Termites do not attack the sound timber. [8]

Uses

Chengal house in the museum in Kuala Terengganu, 2005

The timber is suitable for all forms of heavy construction, railway sleepers, heavy duty furniture, laboratory benches, bridges, marine construction, boat building, telegraphic and power transmission posts and cross arms, piling, mallets, flooring (heavy traffic), decking, vehicle bodies (framework and floor boards), fender supports, cooling towers (structural members), staircase (balusters, carriages, handrails, newels, risers, stringers, treads, bullnoses, round ends and winders), columns (heavy duty), door and window frames and sills, tool handles (impact), carving works and other uses where strength and durability are required. [9]

Chengal in traditional Malay boatbuilding on Duyong Island, 2004

On the Malay Peninsula Chengal has been used as the wood of choice for house and boatbuilding. It is sometimes referred to as the "Malaysian Teak". Despite its extreme strength and hardness, Chengal is highly flexible before it is fully cured, making it the ideal wood for plank bending (boatbuilding). It is also highly resistant to rot, fungi and mildew. In addition, Chengal has a relatively low shrinkage ratio, (only inferior to Teak) which makes it excellent for applications where it undergoes periodic changes in moisture. Chengal, like Teak, has the unusual properties of being both an excellent structural timber for framing, planking, etc., while at the same time being easily worked and finished to a high degree. Due to the oily nature of the wood, care must be taken to properly prepare the wood before gluing.

Chengal may be varnished but does not necessarily need a "finish". The wood will naturally weather to a silver-grey colour similar to Teak. The wood may also be oiled with a finishing agent such as linseed or tung oil. This results in a dark brown finish.

If Chengal is used as a boat deck, it is extremely durable and requires very little maintenance. But it shrinks more than Teak and the deck will therefore develop more leaks and due to its hardness a Chengal deck will be relatively slippery, developing a marble like surface. Chengal decks should only be washed with salt water, and recaulked when needed. This cleans the deck, and prevents it from drying out and the wood from shrinking. The salt helps it absorb and retain moisture, and prevents any mildew and algal growth.

References

  1. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  2. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  3. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  4. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  5. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  6. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  7. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  8. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
  9. ↑ 100 Malaysian Timbers, published by Malaysian Timber Industry Board, 1986, p16/17
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