Wood species
Wallaba wood
Wallaba is a hardwood (Eperua spp.). At 12% moisture content it has a Janka hardness of 2,040 lbf (9,074 N) and it weighs about 58 lb/ft³ (929 kg/m³), 4.8 lb (2.19 kg) per board foot.
Also called: wapa, apa.
Key numbers
- Janka hardness, 12% MC
- 2,040 lbf (9,074 N)
- Green: 1,540 lbf (6,850 N)
- Weight at 12% MC
- 58 lb/ft³ (929 kg/m³)
- 4.8 lb per board foot
- Specific gravity (oven-dry weight)
- 0.78 on green volume
- Shrinkage, green to oven-dry
- 6.9% tangential
- Radial 3.6%, volumetric 10.0%
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4)
Why: From the USDA Wood Handbook, which collected these values from the world literature; wallaba's density is worked from its specific gravity with the Handbook's own equations.
How much wallaba moves
A 12 in wide flatsawn board of wallaba that goes from 6% to 12% moisture content swells about 0.18 in (about 3/16 in, 4.5 mm). Quartersawn, the same board moves about 0.09 in (about 3/32 in, 2.3 mm). Flatsawn faces move 1.9 times as much as quartersawn ones, because the wood shrinks 6.9% around the growth rings but only 3.6% across them.
Worked from the Wood Handbook's shrinkage values (Table 4-4) with its Eq. 13-4; the Handbook gives no movement coefficients for imported woods. Individual boards vary: the Handbook gives shrinkage a coefficient of variation of about 15% (p. 4-11).
Color, grain and working
- Color
- Light to dark red to reddish or purplish brown, with dark, gummy streaks.
- Grain and texture
- Rather coarse texture, typically straight grain.
- Working and character
- Hard and heavy, stronger than shagbark hickory. Dries very slowly and tends to check, split and warp; easy to work despite its density, though gum clogs saws until it is kiln dried. Very durable.
- Uses
- Heavy construction, railroad ties, poles, industrial flooring and tank staves.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-38.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for wallaba from Wood Handbook Table 5-5b (p. 5-25), which the Handbook says were collected from the world literature, on clear, straight-grained specimens. Knots and cross grain make lumber weaker than these clear samples (Handbook Chapter 5).
| Property | Green | 12% MC |
|---|---|---|
| Bending strength (MOR) | 14,300 psi (99 MPa) | 19,100 psi (132 MPa) |
| Stiffness (MOE) | 2,330,000 psi (16.1 GPa) | 2,280,000 psi (15.7 GPa) |
| Crushing strength (compression parallel to grain) | 8,040 psi (55 MPa) | 10,760 psi (74 MPa) |
| Shear parallel to grain | — | — |
A dash means the Handbook prints no value; none is filled in.
Dust and health
- Wood dust is classed as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer, chiefly for cancers of the nose and sinuses.
- NIOSH recommends keeping wood dust exposure to 1 mg/m³ of total dust, as quoted in OSHA's sawmill guidance.
This is what the named authorities publish, not medical advice.
Compare with
Why these numbers
Why these numbers?
The situation
The Wood Handbook prints 2,040 lbf of side hardness at 12% moisture content for wallaba, a value it says was collected from the world literature (Table 5-5b, p. 5-25).
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4) , sources [1]
What that means
Side hardness (Janka) is the load needed to press a 0.444 in (11.28 mm) steel ball halfway into the wood across the grain; a higher number dents less (Handbook p. 5-5).
One source: USDA Forest Products Laboratory, collected from the world literature (its Tables 5-5 and 4-4) , sources [1]
So
The Handbook gives only the green specific gravity (0.78) for wallaba, so it is moved to 12% with the volumetric shrinkage of 10% (Eqs. 4-9 and 4-11), then multiplied by water's density and 1.12 (Eq. 4-14).
Arithmetic: exact by definition , sources [1]
The number
About 58 lb/ft³, or 4.8 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources