Tropical wood · Africa
Okwen wood
Okwen (Brachystegia spp., family Leguminosae) is a tropical timber from Africa. Dry, its Janka hardness is 930–1,430 lbf (4,137–6,361 N), and air-dry it weighs about 34–44 lb/ft³ (545–705 kg/m³). The figures are from the USDA Forest Products Laboratory's Tropical Timbers of the World, pp. 351–352.
Other names, by country: Achi, Ngu, Akolodo (Nigeria), Meblo (Ivory Coast), Naga (Cameroon), Mendou (Gabon).
Key numbers
- Janka hardness, dry
- 930–1,430 lbf (4,137–6,361 N)
- As printed: “Janka side hardness 930-1,430 lb for dry material.”
- Air-dry density
- 34–44 lb/ft³ (545–705 kg/m³)
- Basic specific gravity
- 0.45–0.58 oven-dry weight, green volume
- As printed: “Basic specific gravity (ovendry weight/green volume) varies with species 0.45-0.58; air-dry density 34 to 44 pcf.”
- Shrinkage, green to 12% moisture content
- 3.5% tangential
- Radial 2.5%
- As printed: “Shrinkage green to 12% moisture content: radial about 2.5%; tangential about 3.5%.”
One source: USDA Forest Products Laboratory, Tropical Timbers of the World (Chudnoff, 1979 edition), the only published source read for this wood
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE); crushing strength is compression parallel to the grain. The sheet collects these from published tests: it prints 3 data sets, from different tests and sources, so they can differ widely; all are shown, in the sheet's order, each at the moisture content printed beside it, never restated as 12%.
| Moisture | Bending strength (MOR) | Stiffness (MOE) | Crushing strength |
|---|---|---|---|
| Green | 11,400 psi (79 MPa) | 1.28 million psi (8.8 GPa) | 5,720 psi (39 MPa) |
| 12% MC | 15,200 psi (105 MPa) | 1.53 million psi (10.5 GPa) | 8,270 psi (57 MPa) |
| 12% MC | 12,300 psi (85 MPa) | 1.19 million psi (8.2 GPa) | 6,230 psi (43 MPa) |
A dash means the sheet prints no value; none is filled in.
What the data sheet says
- Color, grain and texture
- 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.
- 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.
- Uses
- Parquet flooring, decorative veneer, general construction where high durability is not required, joinery.
- Where it grows
- A commercial grouping of four species of Brachystegia found in west Africa; common and gregarious in the wetter high forests of Nigeria.
Quoted from Tropical Timbers of the World, pp. 351–352, a USDA Forest Products Laboratory work in the public domain.
Work it out for your project
- Rank woods for flooring with the species picker
Weigh okwen against other woods on hardness, weight, movement and color, every figure from the Wood Handbook.