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Stringybark, Blackdown

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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.

 

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.

Common Form

Sawn

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 - Further Information

Availability of Blackdown stringybark timber products is generally confined to the region in which the species naturally occurs (the Blackdown Tableland in central Queensland).

Availability - Further Information

Native Forest

Shrinkage

Very Low Low Medium High Very High

Tangential :

7.00%

Radial:

Unit Movement Tangential:

Unit Movement Radial:

Strength Group

Very High

High

Reasonably High

Medium High

Medium

Reasonably Low

Low

Very Low

Unseasoned:

S1

S2

S3

S4

S5

S6

S7

Seasoned:

SD1

SD2

SD3

SD4

SD5

SD6

SD7

SD8

Stress Grade

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:

1000kg/m3

Unseasoned:

0kg/m3

Joint Group

Very High

High

Reasonably High

Medium

Low

Very Low

Unseasoned:

J1

J2

J3

J4

J5

J6

Seasoned:

JD1

JD2

JD3

JD4

JD5

JD6

Colour

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

Mechanical Properties

Modulus of Rupture - Unseasoned:

Modulus of Rupture - Seasoned:

Modulus of Elasticity - Unseasoned:

Modulus of Elasticity - Seasoned:

Maximum Crushing Strength - Unseasoned:

Maximum Crushing Strength - Seasoned:

Impact - Unseasoned:

Impact - Seasoned:

Toughness - Unseasoned:

Toughness - Seasoned:

Hardness - Unseasoned:

Hardness - Seasoned:

Durability

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

In-Ground:

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

Above ground:

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

Marine Borer Resistance:

Lyctid Borer Susceptibility:

Not Susceptible

Lyctid Borer Susceptibility - Other:

Termite Resistance:

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:

<250

Bushfire Resistance:

BAL 12.5 and 19 – All AS3959 required applications

Portal Frames

Timber portal frames are one of the most favoured structural applications for commercial and industrial buildings whose functions necessitate long spans and open interiors. As a material choice, timber offers designers simplicity, speed and economy in fabrication and erection.

Timber portal frames offer a strong, sound and superior structure. Structural action is achieved through rigid connections between column and rafter at the knees, and between the individual rafter members at the ridge. These rigid joints are generally constructed using nailed plywood gussets and on occasion, with steel gussets.

From material selection to finishing, this application guide provides a comprehensive overview of the process of using timber in the specification, fabrication and erection of portal frame structures.

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