WA blackbutt has the common name 'yarri'. WA blackbutt is usually a tall tree up to 45 m in height, with diameter at breast height to 1.8 m and a relatively large straight bole. On less favourable, particularly swampy sites, it is a smaller tree of poor form. It has a natural distribution that coincides closely with that of jarrah (E. marginata), from near Perth in the north to Albany on the south coast.
Heartwood is pale yellowish-brown, and the sapwood is sufficiently paler to be distinguishable.
Green density is the density of wood in the living tree, defined as green mass divided by green volume, and useful for estimating transport costs. It varies with season and growing conditions.
Air-dry density is the average mass divided by volume at 12 per cent moisture content (this is the average environmental condition in the coastal capital cities around Australia).
Basic density is oven-dry mass divided by green volume. This measure has the advantage that moisture content variations in the tree during the year are avoided.
:Green density is about 1120 kg/m3, air-dry density about 850 kg/m3, and basic density about 690 kg/m3.
Tangential and radial shrinkage before reconditioning are 10.0 and 5.0 per cent respectively, and after reconditioning 7.0 and 3.5 per cent respectively.
The timber is relatively easy to work, although interlocked grain can make it difficult.
The CSIRO Durability Classes are based on the performance in ground of outer heartwood when exposed to fungal and termite attack.
Class | Life Years |
---|---|
1 | More than 25 |
2 | 15 to 25 |
3 | 8 to 15 |
4 | Less than 8 |
The ratings are not relevant to above-ground use. In late 1996, CSIRO published revised ratings, which include termite susceptibility. Ratings are now available for about seventy species for decay, and for decay plus termites.
:Durability Class based on the CSIRO 1996 ratings is 2 for decay, and 4 for decay + termites. Sapwood is Lyctus-susceptible.
Minimum values (MPa) for strength groups for green and seasoned timber come from Australian Standard AS2878-1986 'Timber - Classification of strength groups'. In grading structural timber, each species is allocated a ranking for green timber of S1 (strongest) to S7, and for seasoned timber SD1 (strongest) to SD8.
MOR is modulus of rupture or bending strength, MOE is modulus of elasticity or 'stiffness', and MCS is maximum crushing strength or compression strength. Hardness refers to the Janka hardness test and is a measure of resistance to indentation.
Minimum values (Mpa) for green timber
Strength Property | S1 | S2 | S3 | S4 | S5 | S6 | S7 |
---|---|---|---|---|---|---|---|
MOR | 103 | 86 | 73 | 62 | 52 | 43 | 36 |
MOE | 16300 | 14200 | 12400 | 10700 | 9100 | 7900 | 6900 |
MCS | 52 | 43 | 36 | 31 | 26 | 22 | 18 |
Minimum values (Mpa) for green timber
Strength Property | SD1 | SD2 | SD3 | SD4 | SD5 | SD6 | SD7 | SD8 |
---|---|---|---|---|---|---|---|---|
MOR | 150 | 130 | 110 | 94 | 78 | 65 | 55 | 45 |
MOE | 21500 | 18500 | 16000 | 14000 | 12500 | 10500 | 9100 | 7900 |
MCS | 80 | 70 | 61 | 54 | 47 | 41 | 36 | 30 |
Where test data were available, they are shown in bold print. Most values are from Bootle (1983), Wood in Australia. Types, properties and uses. (McGraw-Hill), or Julius (1906), 'Western Australian timber tests 1906: The physical characteristics of the woods of Western Australia'.
Where no strength data were available, air-dry density was used in accordance with the Australian Standard AS2878-1986 Timber - Classification of strength groups to predict the strength group. Consequently, the strength values quoted are from the above two tables.
:Green and dry strength groups are S4 and SD5. The more important strength properties are given in the table below.
Property | Units | Green | Dry |
---|---|---|---|
Modulus of Rupture | MPa | 66 | 99 |
Modulus of Elasticity | MPa | 12000 | 13000 |
Max Crushing Strength | MPa | 37 | 65 |
Hardness | KN | 5.5 | 6.9 |
Availability is limited, because a large part of the resource is now conserved in stream reserves. The timber is available in small quantities in Western Australia.
Blackbutt's main use has been in flooring, although in the past it was used for general construction, case manufacture, sleepers, flooring and panelling.