Stringybark, Blackdown

Blackdown stringybark is a durable native Australian hardwood, suitable for a range of engineering and construction applications

Other Names

Eucalyptus sphaerocarpa

Botanical Name

Eucalyptus sphaerocarpa

Common Form
Sawn
Species Type
Hardwood
  • Overview

    • Blackdown stringybark is a native hardwood species growing to a height of 45 metres, with a stem diameter of up to two metres. It is not considered a ‘true’ stringybark, but is named for its fibrous, grey-brown bark. Heartwood ranges in colour from brown to yellow-brown. Sapwood, usually distinct, is a pale brown colour. The texture of Blackdown stringybark timber is even, with slightly interlocked grain. Fine rays are visible with a lens.

    Blackdown stringybark is a durable timber, with a life expectancy of up to 40 years above ground, and 15 to 25 years in-ground. It is termite-resistant in accordance with AS 3660.1, and untreated sapwood is immune to lyctid borer (powder post beetle) attack. The sapwood of this species is, however, readily impregnated with preservatives using commercially available procedures.

    Blackdown stringybark is a very hard timber (rated 1 on a 6-class scale) in relation to both indentation and hand tooling. It is readily worked by machine, and amenable to the use of all standard fastenings and fittings. It may be satisfactorily painted, stained, polished and glued using standard procedures.

    The timber of this species is commonly used in engineering (mining timbers, utility pole cross-arms) and general construction (framing, cladding, flooring) applications. However, commercial availability is generally limited by proximity to Blackdown Tableland in central Queensland, about 150 kilometres southwest of Rockhampton.

     

    Shrinkage

    Very Low Low Medium High Very High
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    Tangential : Provides a simplified rating for tangential shrinkage. This is the measure of the percentage reduction in dimension from the unseasoned to 12% moisture content condition.
    7.00%

    Radial : Radial shrinkage is perpendicular to the growth rings. It is shrinkage in the direction towards the centre of the tree. Measurement is % value

    Unit Movement Tangential: This is the percentage of dimensional change for each 1% moisture content change between about 3% moisture content and the fibre saturation point for the particular species.

    Unit Movement Radial: This is the percentage of dimensional change for each 1% moisture content change between about 3% moisture content and the fibre saturation point for the particular species.

    Strength Group Strength groups are given for unseasoned (S1-S7) and seasoned (SD1-SD8) timber in accordance with AS 2878. S1 and SD1 yield the highest strength and stiffness whereas S7 and SD8 yield the lowest.

    Very High

    High

    Reasonably High

    Medium High

    Medium

    Reasonably Low

    Low

    Very Low

    Unseasoned:

    S1

    S2

    S3

    S4

    S5

    S6

    S7

    S8
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    Seasoned:

    SD1

    SD2

    SD3

    SD4

    SD5

    SD6

    SD7

    SD8
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    Stress Grade A stress grade is defined in AS 1720 as the classification of timber for structural purposes by means of either visual or machine grading. The stress grade indicates the basic working stresses and stiffnesses to be used for structural design purposes. Measured in MPa.

    Structural
    No. 1    		 Structural
    No. 2    		 Structural
    No. 3    		 Structural
    No. 4    		 Structural
    No. 5

    Unseasoned:

    F17

    F14

    F11

    F8

    F7

    Seasoned:

    F27

    F22

    F17

    F14

    F11

    Density per Standard Seasoned density is based on moisture content of 12%. Unseasoned density is an approximation as it depends on the moisture content at the time of measurement. Measured kg/m3.

    Seasoned:

    1000kg/m3

    Unseasoned:

    0kg/m3

    Joint Group The joint group is a classification of the strength of a species in joint design. The values are from 1 (very high strength) to 6 (very low strength).

    Very High

    High

    Reasonably High

    Medium

    Low

    Very Low

    Unseasoned:

    J1

    J2

    J3

    J4

    J5

    J6
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    Seasoned:

    JD1

    JD2

    JD3

    JD4

    JD5

    JD6
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    Colour The colour of seasoned heartwood can vary between species and often within a species. The information provided should be used as a general guide only. In most cases, the colour of sapwood is either a lighter shade of the heartwood or a white/cream colour.

      White, yellow, pale straw to light brown Pink to pink brown Light to dark red Brown, chocolate, mottled or streaky
       
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    Mechanical Properties

    Modulus of Rupture - Unseasoned: This property is a measure of maximum stress which timber can momentarily sustain when loaded slowly and continuously as a beam. Measured in MPa.

    Modulus of Rupture - Seasoned: This property is a measure of maximum stress which timber can momentarily sustain when loaded slowly and continuously as a beam. Measured in MPa.

    Modulus of Elasticity - Unseasoned: This property is of importance in determining the deflection of a beam under load — the greater the stiffness, the less the deflection. Measured in GPa.

    Modulus of Elasticity - Seasoned: This property is of importance in determining the deflection of a beam under load — the greater the stiffness, the less the deflection. Measured in GPa.

    Maximum Crushing Strength - Unseasoned:

    Also referred to as compression strength. This property measures the ability of the timber to withstand loads applied on the end grain. Measured in MPa.

    Maximum Crushing Strength - Seasoned: Also referred to as compression strength. This property measures the ability of the timber to withstand loads applied on the end grain. Measured in MPa.

    Impact - Unseasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.

    Impact - Seasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.

    Toughness - Unseasoned: This is a measure of timber’s ability to resist shocks and blows, and is synonymous with impact strength. It is measured in Nm.

    Toughness - Seasoned: This is a measure of timber’s ability to resist shocks and blows, and is synonymous with impact strength. It is measured in Nm.

    Hardness - Unseasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.

    Hardness - Seasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.

    Durability

    Low Moderate Reasonably High High
    (0 - 5 yrs) (5 - 15 yrs) (15 - 25 yrs) (more than 25 yrs)

    In-Ground: Durability is defined as the inherent resistance of a timber species to decay, or to insect or marine borer attack. All references to durability refer to the heartwood only. A scale of low to high (durability class 4 = low; 1 = high) has been adapted for above and in-ground durability.

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    (0 - 7 yrs) (7 - 15 yrs) (15 - 40 yrs) (More than 40 yrs)

    Above ground: Durability is defined as the inherent resistance of a timber species to decay, or to insect or marine borer attack. All references to durability refer to the heartwood only. A scale of low to high (durability class 4 = low; 1 = high) has been adapted for above and in-ground durability.

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    (0 - 20 yrs, usually < 5) (21 - 40 yrs) (41 - 64 yrs) (More than 60 yrs)

    Marine Borer Resistance: Indicates whether a species is resistant (R) or not resistant (NR) to marine borer attack.

    Lyctid Borer Susceptibility: Indicates whether a species is susceptible (S) or not susceptible (NS) to lyctid borer attack.

    Not Susceptible

    Lyctid Borer Susceptibility - Other:

    Termite Resistance: Indicates whether a species is resistant (R) or not resistant (NR) to termites.

    Resistant

    Fire Properties

    1 - non-combustible 2 - reasonably non-combustible 3 - slightly combustible 4 - combustible

    Fire Properties Group
    Number:

    Group Number - Other:
    3 if used on MDF or particleboard

    Average Specific Extinction Area: This value is determined by the volume of smoke measured over the mass loss of the tested sample per test carried out in accordance with ‘Cone Calorimeter Test’ AS/NZS 3837. It is measured in units of m2/kg.
    <250

    Bushfire Resistance: Naturally bushfire-resisting timbers are those with inherent bushfire-resisting properties. Some species have been tested and a number are in the process of being tested and are measured by Bushfire Attack level (BAL). BAL -12.5: Ember attack, BAL – 19: Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 12.5 and 19 kWm3, BAL – 29: Increasing levels of ember attack and burning debris ignited by windborne embers together with increasing heat flux between 19 and 29 kWm3.
    BAL 12.5 and 19 – All AS3959 required applications
    Appearance

    Blackdown stringybark timber is of medium and even texture, with slight interlocking of grain and fine rays visible with a lens. Heartwood ranges in colour from brown to yellow-brown. Sapwood, usually distinct, is a pale brown colour.

    Common Applications

    Blackdown stringybark is commonly used in engineering applications such as mining timbers and utility pole cross-arms. It is also commonly used for unseasoned framing, flooring, cladding and general building construction purposes.

    Workability

    Blackdown stringybark is relatively easy to season and work, but due to its hardness is best worked by machine. It readily accepts paint, stains, glues, and polish. No difficulties have been encountered in the use of standard fittings and fastenings.

    Origin of timber
    QLD
    Readily Available
    QLD
    Availability of Blackdown stringybark timber products is generally confined to the region in which the species naturally occurs (the Blackdown Tableland in central Queensland).
    Source of timber
    Native Forest
    a large room with rows of chairs

    Portal Frames

    For buildings that require large spans and column free interiors, timber portal frames provide one of the most aesthetically pleasing solutions. Utilising modern engineering technology, portal frame design transforms timber into a highly effective, efficient and economical structural product.

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