Darwin stringybark

Darwin stringybark's heartwood is pale reddish-brown with wide sapwood similar to forest red gum. Density (990-1200) kgm3 being hard, heavy and stiff, with exceptionally good impact properties comparable to the ironbarks.

Other Names

No other published names are in use

Botanical Name

Eucalyptus tetrodonta

Common Form
Sawn
  • Overview

    • Sapwood pale yellow or white, fairly wide and not always clearly demarcated from the reddish-brown or pale red heartwood.  Texture (referring to vessel size) medium.  Grain mainly straight.  The figure is not prominent, and growth rings occasionally tending to distinct. The species is widely distributed through northern Australia from Queensland to Western Australia north of latitude 16oS; trees grow from close to sea level up to 300m.  Best growth occurs on moderately deep, well drained sandy soils.  Represents one of the larger species in the Northern Territory which produces good milling timber.  The species is also recommended for tropical forestry.  

    Suitability for pulp and paper and composites:

    The basic density of the species is higher than what paper manufacturers generally desire, and CSIRO studies have indicated that pulp yields from natural stands are low. The high basic density also makes the species less desirable for composite wood products such as laminated veneer lumber and medium density fibreboard but quite suitable for solid-wood products.

    Wood characteristics:

    Timber is of high density similar to that of the ironbarks making it hard, heavy and stiff, with exceptionally good impact properties.  It is not easy to work with machine operations and it is difficult to cut with hand tools.  Material tends to ride on planer cutters; straighter grain usually produces good surfaces.  A 15o cutting angle is recommended for stock with interlocked grain.  Quartersawn boards dry fairly rapidly provided mild drying schedules are used.  The timber is fissile (easy to split), and glues fairly well.  Wearing and weathering properties are good.  Sapwood is lyctus susceptible, heartwood occasionally attacked by termites.  Sapwood is probably permeable, but the heartwood is extremely difficult to impregnate.  The wood is often used in hewn or as rounds.

    REFERENCES:

    1  W.G. Keating and E. Bolza. (1982) Characteristics, properties and uses of timbers. Vol. 1., South-east Asia, Northern Australia and the Pacific. Inkata Press

    2  W.J. Smith, W.T. Kyneston, M.L. Cause and J. G. Grimmett (1991) Building timbers.  Technical Pamphlet No. 1, Queensland Forest Service, Department of Primary Industries 

    3  B. Budgeon (1981)/ The shrinkage and density of some Australian and South-East Asian timbers.  Tech paper (2nd series) No. 38, Division of Building Research, CSIRO, Australia

    4  E. Bolza and N.H. Kloot (1963) The mechanical properties of 174 Australian timbers.  Tech paper No. 25, Division of Building Research, CSIRO, Australia 

    5  T. J. Venn (2003) Potential markets for logs and sawn timber from Darwin stringybark forests of Cape York Peninsula.  Marketing of farm-grown timber in tropical North Queensland : conference proceedings, 18 June 2003

    FOOTNOTES:

    SHRINKAGE - tangential and radial shrinkages after reconditioning, Values before reconditioning are slightly higher indicating low degree of wood collapse

    DENSITY - Seasoned - after reconditioning

    MOISTURE CONDITION - No specific data is available for seasoned material.  The seasoned values shown are estimated from corresponding green values from the Strength grouping classification as per (Ref 1)

     

    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.
    4.90%

    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.
    3.80%

    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:

    F22

    F22

    F17

    F14

    F11

    Seasoned:

    F34

    F27

    F22

    F17

    F14

    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:

    1090kg/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.
    145

    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.
    108

    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.
    16.3

    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.
    18.7

    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.
    73.8

    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.
    81

    Impact - Unseasoned: Provides the Izod value, which is the energy taken in joules (J) to fracture the timber.
    73.8

    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.
    High - 25 Nm and above

    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.
    High - 25 Nm and above

    Hardness - Unseasoned: Refers to the Janka hardness test and is a measure of timber’s resistance to indentation.
    9.5

    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.

    		 Check mark
    (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.

    		 Check mark
    (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.

    Susceptible

    Lyctid Borer Susceptibility - Other:

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

    Resistant

    Fire Properties

    Appearance

    Sapwood pale yellow or white, fairly wide and usually clearly demarcated from the reddish-brown or pale red heartwood.  Texture (referring to vessel size) medium.  Grain mainly straight.  The figure is not prominent, and growth rings occasionally tending to distinct.

    Common Applications

    Heavy structural; heavy flooring; mine timber; ship and boat building; handles and ladders; agricultural implements; joinery; sleepers; poles and piles; cross arms.

    Workability

    It is not easy to work with machine operations and it is difficult to cut with hand tools.  Material tends to ride on planer cutters; straighter grain usually produces good surfaces.  A 15o cutting angle is recommended for stock with interlocked grain.

    Origin of timber
    QLD
    On Cape York Peninsula there are about 1.7 Mha of eucalypt forests with commercially attractive timber species on land tenures other than National Park.
    The Queensland Department of Primary Industries - Forestry (DPI-Forestry) considers the stands of timber in the Darwin stringybark (Eucalyptus tetrodonta) forests on Cape York Peninsula (CYP) to be the largest remaining forest resource in Queensland.
    Source of timber
    Native Forest
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