Shorea laevis

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Shorea laevis
Systematics
Eurosiden II
Order : Mallow-like (Malvales)
Family : Wing fruit family (Dipterocarpaceae)
Subfamily : Dipterocarpoideae
Genre : Shorea
Type : Shorea laevis
Scientific name
Shorea laevis
Ridl.
The 274 meter long pedestrian bridge, "Henderson Waves" in Singapore ; with a bottom made entirely of Yellow Balau
Garden furniture from Yellow Balau

Shorea laevis ( Syn . : Hopea laevifolia Parijs , Shorea laevifolia Endert , Shorea rogersiana Raizada & Smithinand ) is a species ofthe wing fruit family (Dipterocarpaceae). It occurs inthe primary rainforest in Southeast Asia .

The trade names for the wood are Yellow Balau or Bangkirai (also for other Shorea species) and not clearly Balau ; under the trade name Bangkirai z. B. also the wood types Red Balau ( Shorea spp.), Keruing ( Dipterocarpus spp.), White Seraya ( Parashorea , Shorea ) and Merawan ( Hopea spp.) Sold. The wood is hard and durable, which is why Shorea laevis is also grown outside of its natural range and traded internationally.

features

Shorea laevis grows as a tree that reaches a height of up to 75 meters and a diameter of about 1.5 meters at chest height . Root approaches or sometimes high buttress roots are formed. The bark is brown and easily cracked and flaky. The tree carries a resin ( dammar ).

The alternately arranged, short-stalked leaves are simple, glabrous and shiny. They are egg-shaped to elliptical, slightly leathery, with entire margins and pointed and up to 6.5-10 centimeters long. The stipules are about 8 millimeters long.

The approximately 5 millimeters large, yellowish-green, stalked flowers are arranged in terminal or axillary paniculate inflorescences. The hermaphrodite flowers, with two small, sloping bracts , are radially symmetrical and five-fold with a double flower envelope . Many stamens and a top constant, hairy ovary with a "stylopodium" and recently, bald pen available. The partly bearded anthers have a hairy appendage.

The approximately 10-15 millimeters long, egg-shaped nuts have five, three longer and two shorter, about 40-65 millimeters long wings, with which they are spread by the wind .

Wood

The heartwood appears when fresh yellowish brown to greenish, often darkens to olive-brown after. The core is not always clearly separated from the lighter sapwood . However, the color varies a lot. The growth zone boundaries are not pronounced, dry wood has no characteristic odor. The wood, which is predominantly homogeneous in color and structure, has a medium to coarse texture and high density.

Occurrence

The natural range of Shorea laevis includes Myanmar , Thailand , the Malay Peninsula , Sumatra and Borneo . The trees grow in undisturbed primary forest up to an altitude of around 600 meters on sandy or clay soils . They prefer slopes and ridges, but also occur on alluvial land . Shorea laevis is grown outside of its natural range in India, Pakistan , Sri Lanka, Laos , Vietnam , Cambodia, and the Philippines .

use

The Yellow Balau wood is heavy and very weather resistant; it dries slowly and is prone to surface cracks. It has high strength values ​​that are 50% higher than oak ; therefore it is difficult to edit. The bulk density (approx. 800–975 kg / m 3 ) is 20 to 40% higher than that of oak. The heartwood is very resistant to fungi and insects. Yellow Balau is one of the toughest woods, even under tropical conditions it is durable. The classification of the natural durability against wood-destroying fungi according to EN 350-2 is in class 2 (permanent). Life expectancy under moderate climatic conditions is 15 to 25 years.

The wood is used for all types of buildings, especially outdoors such as B. for bridge and hydraulic engineering, usually without any impregnation. In India it is mainly used as railway sleepers, in Malaysia as masts, pit timber and in shipbuilding, in Europe and elsewhere as construction timber for dock and harbor construction, quays , driven piles , terrace coverings and garden furniture.

Some of the trade names are: Yellow Balau, Sal (India), Balau ( Sarawak ), Bangkirai, Kumus (Indonesia), Selangan Batu ( Sabah ), Aek, Ak, Tang, Teng or Chan (Thailand), Gisok or Yakal (Philippines) . So Balau and Selangan Batu are Malay terms. It is not to be confused with the actual Sal ( Shorea robusta ).

The wood is only rarely available with an FSC certificate. An origin from overexploitation cannot be ruled out.

Usage characteristics

When constructing with Bangkirai there are several points to consider:

  • Resin galls (narrow gaps filled with white crystals) appear very rarely .
  • Crack formation: In order to keep the fine crack formation as low as possible during storage, especially on the head sides, these are often coated with wax at the factory. You therefore have to cut the boards during assembly.
  • Slight surface cracks (they can be caused by weathering) have no static effects.
  • Graying: Like any other type of wood, Bangkirai also turns gray. In order to get the initial color, you can oil the surface (see wood preservatives ).
  • Bleeding: There may be leakage of ingredients when using Bangkirai outdoors. Surrounding materials should e.g. B. be protected by foil. In the balcony area you should pay particular attention to the leakage of the ingredients. (Contamination of the facade possible)
  • Tannins in Bangkirai react with ferrous metals, black spots form. With stainless steel this can be circumvented screws.
  • Bangkirai is too hard and too dense to nail. Even screws must always be pre-drilled. You can saw with any normal saw. However, the tool life is reduced.
  • When planing, the alternating twist can cause tearing.

swell

Web links

Individual evidence

  1. ↑ Henderson Waves at Visit Singapore, accessed October 13, 2019.
  2. ↑ Jean Gérard et al. a .: Tropical Timber Atlas. Éditions Quæ, 2017, ISBN 978-2-7592-2798-3 , pp. 153 ff, pp. 958 f, 962 f, 966, 970, 991, limited preview in the Google Book search.
  3. ↑ Heinz M. Hiersig : Lexikon production technology process engineering. Vol. 2, Springer, 1995, ISBN 978-3-642-63379-9 , pp. 452, 455.