Wood species
Ipe wood
Ipe is a hardwood (Tabebuia spp., lapacho group). At 12% moisture content it has a Janka hardness of 3,680 lbf (16,369 N) and it weighs about 70 lb/ft³ (1,119 kg/m³), 5.8 lb (2.64 kg) per board foot.
Also called: lapacho, guayacan.
Key numbers
- Janka hardness, 12% MC
- 3,680 lbf (16,369 N)
- Green: 3,060 lbf (13,612 N)
- Weight at 12% MC
- 70 lb/ft³ (1,119 kg/m³)
- 5.8 lb per board foot
- Specific gravity (oven-dry weight)
- 0.92 on green volume
- Shrinkage, green to oven-dry
- 8.0% tangential
- Radial 6.6%, volumetric 13.2%
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; ipe's density is worked from its specific gravity with the Handbook's own equations.
How much ipe moves
A 12 in wide flatsawn board of ipe that goes from 6% to 12% moisture content swells about 0.21 in (about 7/32 in, 5.2 mm). Quartersawn, the same board moves about 0.17 in (about 5/32 in, 4.2 mm). Flatsawn faces move 1.2 times as much as quartersawn ones, because the wood shrinks 8.0% around the growth rings but only 6.6% 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 olive brown heartwood; wide yellowish gray or gray-brown sapwood.
- Grain and texture
- Fine to medium texture; grain straight to very irregular and often narrowly interlocked.
- Working and character
- Very heavy; dry heartwood generally sinks in water. Moderately hard to machine but can be planed glassy smooth. Very strong, with hardness two to three times white oak, and highly resistant to decay and termites (not marine borers).
- Uses
- Decks, heavy-duty flooring, railroad ties, turnery, tool handles and decorative veneer.
Adapted in our own words from the Wood Handbook, Chapter 2, p. 2-25.
Strength
Bending strength is the modulus of rupture (MOR); stiffness is the modulus of elasticity (MOE). Values for ipe from Wood Handbook Table 5-5b (p. 5-23), 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) | 22,600 psi (156 MPa) | 25,400 psi (175 MPa) |
| Stiffness (MOE) | 2,920,000 psi (20.1 GPa) | 3,140,000 psi (21.6 GPa) |
| Crushing strength (compression parallel to grain) | 10,350 psi (71 MPa) | 13,010 psi (90 MPa) |
| Shear parallel to grain | 2,120 psi (15 MPa) | 2,060 psi (14 MPa) |
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 3,680 lbf of side hardness at 12% moisture content for ipe, a value it says was collected from the world literature (Table 5-5b, p. 5-23).
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 (0.92) for ipe, so it is moved to 12% with the volumetric shrinkage of 13.2% (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 70 lb/ft³, or 5.8 lb per board foot (1/12 ft³), at 12% moisture content.
Arithmetic: exact by definition
Sources