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Veneering of Plantation Grown Subtropical
Species from Thinning Experiments
Anton Zbonak
Queensland Department of Agriculture, Fisheries and Forestry
Brisbane, Australia
SWST Convention, Zvolen 23-27 June 2014
© State of Queensland, 2013
Drivers for plantation hardwood R&D
• Native hardwood forest logging from Crown lands phased out by 2023
• Plantation to provide substitute resource, around 20-year rotation
• Queensland government are expecting the private sector to establish
and manage the plantations
• Limited hardwood plantations established until 2000
© State of Queensland, 2013
Opportunities for small diameter trees
Sawn timber
• Log size and quality make efficient processing difficult
• Low recovery (8-18%)
Power distribution poles
• Limited by available log size and quality
• More suited to final harvest
Veneer based composite products
• High recovery of product
• Opportunities to use thinnings & final harvest
• Veneer: quick and easy to dry
• Existing products and opportunities for new products
© State of Queensland, 2013
Current plantation estate in Queensland
• The subtropical eucalypt estate totals about 116,000 ha with over 54,000
ha of spotted gum (CCV) and Eucalyptus dunnii
© State of Queensland, 2013
• Two species – Corymbia citriodora subsp. variegata (CCV) and Eucalyptus dunnii
• Two regions:
• Ellangowan in northern New South Wales - wetter more productive site
• Kingaroy in Queensland - drier site
Site Species
Mean annual
rainfall
(mm)
Age
thinnedHarvest age
Ellangowan CCV 1096 7y 9m 10.5
Ellangowan E. dunnii 1096 7y 9m 10.5
Kingaroy CCV 783 6y 9m 10.5
Kingaroy E. dunnii 783 6y 9m 10.5
• Three thinning treatments:
• 300 spha
(5 trees/tmt 2 heights)
• 500 spha (not sampled)
• 900 spha - unthinned
(5 trees/tmt 2 heights)
Material - Thinning trials
© State of Queensland, 2013
Material and Methods
E. dunnii CCV
low % of heartwoodAcoustic velocity measurement
Forest inspectors
© State of Queensland, 2013
Billet end splitting
0
2
4
6
8
10
12
Lo
g e
nd
sp
lit
are
a i
nd
ex
Thin Unthin Mean
Ellangowan Kingaroy Ellangowan Kingaroy
CCV CCVE. dun E. dun CCV CCVE. dun E. dun
After 24 hrs After steam
• No splitting issues for CCV
• E. dunnii is splitting prone species – adverse effect on veneer quality
wet site dry site wet site dry site
24 hr after felling 96 hr after felling After steaming
© State of Queensland, 2013
Billet dynamic stiffness
10000
15000
20000
25000
Bu
tt b
ille
t M
OE
(M
Pa)
Thin Unthin Mean
Ellangowan
CCV CCVE. dun E. dun
Kingaroy
10000
15000
20000
25000
To
p b
ille
t M
OE
(M
Pa)
Thin Unthin Mean
Ellangowan
CCV CCVE. dun E. dun
Kingaroy
• No clear effect of thinning treatments
• E. dunnii significantly lower billets stiffness
• Evident site effect on stiffness, lower for drier site
• Top logs o average 10% and 20% stiffer than butt log (CCV and E.
dunnii)
butt log top log
wet site dry sitewet site dry site
© State of Queensland, 2013
Peeling using spindleless lathe
Maximizing product recovery from small logs
45 mm core
© State of Queensland, 2013
Overall gross recoveries
• Ranging from 35 to 80% - double or triple recoveries from sawing
similar diameter logs
• No clear effect of thinning treatments on recoveries
• Kingaroy (dry site) lower in recoveries – effect of smaller trees
• Splitting did not affect veneer recovery
30
40
50
60
70
80
90
Ven
eer
gro
ss r
eco
very
(%
)
Thin Unthin Mean
Ellangowan
CCV CCVE. dun E. dun
Kingaroy
30
40
50
60
70
80
90
Ven
eer
gro
ss r
eco
very
(%
)
Thin Unthin Mean
Ellangowan
CCV CCVE. dun E. dun
Kingaroy
butt log top log
wet site dry site wet site dry site
© State of Queensland, 2013
Grade recovery
• Veneer sheets graded according to AS/NZ 2239: 2008
© State of Queensland, 2013
Veneer grade distribution
• Consistently better grade for butt logs
• Evident effect of site – CCV better grades from wet site
• Indication that thinned plots produced veneers of higher grades
• The majority of D-grade quality is not unexpected given the known presence
of knots and other defects that are present in plantation hardwood trees of
the size and age processed
0%
20%
40%
60%
80%
100%
Thin Unthin Thin Unthin Thin Unthin Thin Unthin
CCV E.dun CCV E.dun
Ellangowan Kingaroy
Dis
trib
uti
on
rela
ted
to
bille
t vo
lum
e
Grade D
Grade C
Grade B
Grade A
0%
20%
40%
60%
80%
100%
Thin Unthin Thin Unthin Thin Unthin Thin Unthin
CCV E.dun CCV E.dun
Ellangowan Kingaroy
Dis
trib
uti
on
rela
ted
to
bille
t vo
lum
e
Grade D
Grade C
Grade B
Grade A
butt log top log
wet site dry site wet site dry site
© State of Queensland, 2013
Acoustic veneer stiffness assessment
1.55 m
veneer sheet
• Veneer assessment samples obtained subsequently after each 1.55 m veneer sheet
• Samples assessed for acoustic stiffness and density
Veneer assessment sample
© State of Queensland, 2013
Acoustic veneer stiffness with cambial age
5000
8000
11000
14000
17000
20000
23000
4 5 6 7 8 9 4 5 6 7 8 9
Kingaroy Lismore
Cambial age (yrs)
Ve
ne
er
MO
E (
MP
a)
CCV - Thinned CCV - Unthinned E.dunnii - Thinned E.dunnii - Unthinned
• CCV is stiffer than E. dunnii; dunnii regarded as pulp species displays high
stiffness despite its low density
• Evident effect of site for both species, no clear effect of thinning
• MoE values above average stiffness of radiata pine
Ellangowan
Drier site Wet site
Average MoE
of mature radiata pine
© State of Queensland, 2013
E. dunnii drier E. dunnii wetter
Effect of dry period on MOE drop
5000
9000
13000
17000
21000
25000
2 4 6 8 10
Cambial age
Ven
eer
MO
E (
MP
a)
Tree 1
Tree 2
Tree 3
Tree 5
5000
9000
13000
17000
21000
25000
2 4 6 8 10
Cambial age
Ven
eer
MO
E (
MP
a)
Tree 1
Tree 2
Tree 3
Tree 4
Tree 5
© State of Queensland, 2013
Predicting veneer stiffness using standing tree acoustics
7000
11000
15000
19000
23000
3.0 3.5 4.0 4.5 5.0
Fakopp AV (km.s-1
)
Ve
ne
er
av
era
ge
MO
E (
MP
a)
CCV
E. dunnii
R2=0.85
Standing tree acoustics can provide reliable estimate
of the quality of the veneer stiffness
© State of Queensland, 2013
Concluding remarks
• Veneering is suitable option for processing of small diameter plantation
resource, maximizing the recovery
• Thinning treatment not affecting veneer stiffness, there are site
differences – less stiff on drier, less productive site
• Both species achieving high values of veneer stiffness – resource suited
to structural veneer products rather than appearance products
• Veneers have attributes suited to engineered wood products (plywood,
LVL,…) and opportunities for novelty products
• Gluability of veneer sheets needs to be explored further
© State of Queensland, 2013
AcknowledgementAcknowledgements
• Collaboration effort of DAFF Forestry Science teams and Southern Cross University
• Sites accessed through Forest Enterprises Australia Ltd
http://www.daff.qld.gov.au/29.htm