Wooden House Article:
Properties of Bangkirai Wood
Botanical Name:
Shorea laevis Ridl. (Syn. S. laevifolia Endert),
Dipterocarpeceae family.
Local Names:
Bangkirai, Yellow Balau, Balau Kuning, Selangan batu, Anggelam, balau kumus, selangan batu kumus, thakian-samphon, mikai, selangan kumus, kumus, penapak, benuas, bangkirai, balau tanduk, chan
Other Names:
Bangkirai, Yellow Balau (UK, USA, Fr, Sp, It, Sw. NI, Gm).
Yellow Balau is usually used in Malaysia and Bangkirai is usually used in Indonesia.
Geographical Distribution:
All over Kalimantan, Indonesia
Habitus:
The tree height may reach 50 m, the length of the clear bole is 35 to 40 m, the diameter is 100 cm and over. The buttress is as high as 2 m. The outer bark is grey, red or brown, sometimes even dark red with grooves and peels off in small thin pieces. The bark contains dark yellow resin.
General Characteristics
Colour:
The Heartwood is brownish yellow, the sapwood yellowish pale light brown.
Texture:
Wood texture ranges from fine to rather coarse.
Grain:
The grain is straight or interlocked.
Touch:
The wood surface is smooth or alternately smooth and rough owing to the interlocked grain.
Gloss:
The wood surface is glossy.
Figures:
The radial section shows stripes in a lighter colour.
Structure
Vessels:
Most vessels are solitary. A small part of them are in groups of 2 to 4 in radial direction, sometimes in tangential and oblique lines. They are round or oval, have a diameter of 1 00 to 300 ?? a frequency of 2 to 10 per Sq mm , and contain much tylosis. The perforation plates are simple.
Parenchyma:
The parenchyma are of the paratracheal type in the form of complete or incomplete borders to the vessels. There are also apotracheal parenohyma in the form of short, tangential bands besides diffuse parenchyma.
Rays:
The rays are homogenous, fine and short, and have a frequency of 6 to 8 per mm. They sometimes contain a brown deposit.
Intercellular canals:
The Intercellular canals are almost always smaller than vessels, occasionally of the same size. They are arranged in long series, and contain white resin.
Fibres:
The fibres are 1,203 long with a diameter of 19.9;
wall thickness of 1.9 and lumen diameter of 16.1.
Physical Properties
Specific gravity:
0.91 (0.60 - 1.16) g/cm3
Strength class:
I – II
Shrinkage:
Shrinkage to oven-dry condition is 4.5 % ( R ) and 8.3 % ( T )
Fibre Saturation Point:
23 %
Mechanical Properties
| Properties | Value | Value |
| Bending strength | 150 mPa | 21,756 psi |
| Modulus of elasticity | 22,940 mPa | 3,327 1000psi |
| Crushing strength | 85 mPa | 12,328 psi |
| JANKA Hardness | 7.99 kN | 1,798 lbs force |
| Note: at 12% moisture content | ||
Chemical Properties
| Chemical Content | Value |
| Cellulose | 62.9 % |
| Lignin | 24.0 % |
| Pentosan | 16.8 % |
| Ash | 1.0 % |
| Silica | 0.4 % |
| Solubility | Value |
| Alcohol – benzene | 3.0 % |
| Cold water | 0.8 % |
| Hot water | 2.6 % |
| 1 % NaOH | 10.9 % |
Durability and Treatability
Durability:
Fungi - Class 2 - Durable
Dry Wood Borers - Heartwood durable
Termites - Class D - Durable
Treatability:
Bangkirai wood is difficult to treat.
Drying
2.5 cm and 4 cm thick Bangkirai boards are kiln dried from 50% to 15% in respectively 6 and 9 days in a drying temperature of 43 degrees Centigrade to 71 degrees Centigrade and a relative humidity of 84% to 38%. Bangkirai wood is difficult to dry as it easily splits, checks, and deforms.
Working Properties
Despite its hardness, bangkirai is not so difficult to work, e.g., with hardened tipped saws or it can be planed smoothly with small cutting angle. Holes should be drilled before nailing to prevent splitting.
Uses
Due to its high strength and durability,- bangkirai wood is used for heavy construction under roof as well as in the open, such as bridges, railway sleepers, electric poles, flooring, marine construction, boat building, vehicular bodywork and housing.
Source: Data are from Indonesia Wood Atlas Volume I, 1989; Department of Foresty Agency for Forestry Research and Development Forest Product Research and Development Centre Bogor-Indonesia.
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