Brachystegia spp.
Family: Leguminosae
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Okwen

 

Other Common Names: Achi, Ngu, Akolodo (Nigeria), Meblo (Ivory Coast), Naga (Cameroon), Mendou (Gabon).

 

Distribution: A commercial grouping of four species of Brachystegia found in West Africa; common and gregarious in the wetter high forests of Nigeria.

 

The Tree: Tall, emergent 120 to 150 ft in height, boles are straight and cylindrical, trunk diameter 4 to 7 ft above the buttresses.

 

The Wood:

General Characteristics: Heartwood light to dark brown; sapwood yellow to yellowish brown, well defined.  Texture medium to coarse; grain usually deeply interlocked producing a pronounced roe figure; luster high.

 

Weight: Basic specific gravity (ovendry weight/green volume) varies with species 0.45 to 0.58; air-dry density 34 to 44 pcf.

 

Mechanical Properties: (2-cm standard)

 

Moisture content   Bending strength   Modulus of elasticity   Maximum crushing strength

            (%)                  (Psi)                            (1,000 psi)                   (Psi)

Green (42)                   11,400                         1,280                           5,720

12%                             15,200                         1,530                           8,270

 

12% (41)                     12,300                         1,190                           6,230

 

Janka side hardness 930 to 1,430 lb for dry material.

 

Drying and Shrinkage: Dries rather slowly with a marked tendency to check and warp. Kiln schedule T6-D2 is suggested for 4/4 stock and T3-D1 for 8/4.  Shrinkage green to 12% moisture content: radial about 2.5%; tangential about 3.5%.  Movement in service is rated as medium.

 

Working Properties: Difficult to saw because of gumming of teeth, blunting may be serious, machines moderately well, good turning characteristics, difficult to plane to a smooth surface because of severe tearing of grain in B. nigerica.

 

Durability: Heartwood is rated as moderately durable, sapwood liable to attack by powder-post beetles.

 

Preservation: Heartwood is extremely resistant to treatment, sapwood is permeable.

 

Uses: Parquet flooring, decorative veneer, general construction where high durability is not required, joinery.

 

Additional Reading: (3), (9), (41), (42)

 

3. Bolza, E., and W. G. Keating.  1972.  African timbers-the properties, uses, and  characteristics of 700   species.  CSIRO.  Div.  of Build.  Res., Melbourne, Australia.

9. Farmer, R. H. 1972.  Handbook of hardwoods.  H. M. Stationery Office.  London.

41. Nigeria: Dep.  For.  Res.  1966.  Brachystegia kennedyi (Okwen).  For.  Prod.  Res.  Rep.  Dep.  For.          Res.  Nigeria No.  FPRL/7.

42. Nigeria: Dep.  For.  Res.  1966.  Brachystegia nigerica (Okwen).  For.  Prod.  Res.  Rep.  Dep.  For.          Res.  Nigeria No.  FPRL/8.

 

From: Chudnoff, Martin. 1984. Tropical Timbers of the World. USDA Forest Service. Ag. Handbook No. 607.