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Intermountain Weight Scaling Methods
Jarred D. Saralecos and Robert F. Keefe Inland Northwest Growth and Yield Cooperative
March 25, 2014
Weight Scaling: Using weight as a unit of measure to determine
the value of logs for buying and selling
Sampling loads for weight and scaled volume to develop weight to volume conversions for future weigh-only loads
Weight scaling is a relatively unexplored scaling method for the Inland Northwest
Compelling Questions: What factors are most important in determining
weight to volume conversions for scaling?
How viable is weight scaling over time (e.g. are trees and environments changing enough to alter relationships)?
What are the effects of moisture loss from felled sawlogs on weight scaling?
J. Saralecos, University of Idaho Experimental Forest, 2013
Strengths and Weaknesses of Weight Scaling
Strengths Tangible to everyone Cheaper than traditional scaling Faster truck turn-times at mill Good correlation with volume
Weaknesses Difficult to determine conversions
- Mixed loads: species/sorts - Variability within species/sort -Moisture content - Heartwood to sapwood ratio
Some scaling is still required Does not measure all value drivers - Diameter, length, defects, grade
Unknowns
Overview
Current Practices
Future
Current Research
Intermountain West
weight scaling
Two UI weight
scaling studies
Where weight
scaling is headed
J. Saralecos, University of Idaho, 2013
Weight Scaling Review
Current Practices
Total scaled volume
÷
Total weighed volume
=
Weight-to-Volume Conversion
J. Saralecos, University of Idaho, 2012
Weight Scaling Review
Current Practices
• One conversion for each supervisory district
• Updated Yearly
• Does not vary by season, species, product type, or defect
• No conversions for cedar products, poles
Weight Scaling Review
Current Practices
• One conversion for each supervisory district
• Updated Yearly
• Does not vary by season, species, product type, or defect
• No conversions for cedar products, poles
J. Saralecos, University of Idaho, 2013
Brad French, Iron Pine Logging, 2013
Study One: U of I Moisture Loss
Investigate moisture loss rates in harvested sawlogs and their affect on weight scaling
Water commonly makes up over half of the wet (green) weight
Sawlogs decked prior to transport are subjected varying amounts of drying and moisture loss
Brad French, Iron Pine Logging, 2013
J. Saralecos, University of Idaho, 2013
Methods
Felled 30 Douglas-fir (Pseudotsuga menziesii) in 3 size classes 5-10, 10-15, 15-20 inches DBH
2 treatments 1) Cut-to-length 2) Whole tree
Sample cores were collected on alternate days through a 28 day period
Cores were dried and weighed to obtain moisture content
U of I Moisture Loss Research Project
U of I Moisture Loss Research Project
Methods cont.
Treatment 1 Treatment 2 Coring Diagram Weight Sampling
Drying
J. Saralecos, University of Idaho, 2013
Study Results
Moisture loss was significantly affected by:
Stem size class – Larger stems lost moisture slower compared to smaller stems
Treatment type – Stems containing limbs had greater loss than stems with removed limbs
Environmental factors – Relative humidity (RH) and vapor pressure deficit (VPD)
Results
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2 4 6 8 10 12 14 16 18 20 22 24 26 28
Mo
istu
re C
on
ten
t (%
)
Days After Harvest
Rate of Moisture Loss by DBH
15-20 in. DBH 10-15 in. DBH 5-10 in. DBH
The moisture content (MC) of stem wood in the days following harvesting. Mean MC values for trees by DBH on a given sampling date are shown as solid shapes and error bars show standard errors (SE).
Results
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Mo
istu
re C
on
ten
t (%
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Days After Harvest
Mean Stem Moisture Content vs Relative Humidity
Mean sample tree MC (%) Mean site relative humidtiy (%)
The changes in stem wood moisture content and site relative humidity are shown over the duration of the study. Mean moisture contents and relative humidity are shown in solid shapes with error bars showing SEs.
Results
y = 0.7655e-0.048x R² = 0.8433
y = 0.7447e-0.061x R² = 0.8605
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2 4 6 8 10 12 14 16 18 20 22 24 26 28
Mo
istu
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)
Days After Harvest
Effect of Treatments on Moisture Content
Treatment 1 Top Treatment 2 Top
Expon. (Treatment 1 Top) Expon. (Treatment 2 Top)
Figure shows the mean moisture content of stem wood separated by treatment type and stem location in the time following harvesting. Treatment 1 represented a cut-to-length harvesting system and Treatment 2 a whole-tree system. The results focused on the MC in the upper portions of the stems underneath the crowns.
Economic Impacts
2 Days
4 Days
3 Days
3.1 tons = $226.27
1.2 tons = $87.56
2.5 tons = $182.60
Idaho DFL $400/mbf
State W-V Avg. 5.48 tons/mbf
Extreme Case Scenario
Avg. truck weight 27.3 tons
Google Images
Study Two: Updating W:V Conversion Factors
Environmental and physical characteristics affecting weight to volume relationship for commercial sawlogs
J. Saralecos, University of Idaho, 2013
Methods
Project Completion: Late April 2014
• 7900 scaled loads from across Idaho
• Investigating climate data (ppt & temp)
• Also looking at species and season
• Working to make conversions more accurate and understandable
Results
Large variation across season and species
W:V Conversions
Limited variation between supervisory districts
Cubic is more closely correlated to weight than Scribner
Defect is highly predictable among delivered loads
16” SED = 16
17” SED = 18
16” SED = 22.34
17” SED = 23.78
Results
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% C
han
ge
from
Av
erag
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Seasonal Quarters
WRC DFL GFHAF LPPP
Current Results
Truckload net weight (tons)
Scal
ed T
ruck
load
Vo
lum
e (
mb
f)
Weight Scaling Conclusions
Weight works best when:
Timber is consistent
Loads are delivered in like-valued sorts
Scaling is used to establish volume and value
The purchaser and seller understand it well and use cubic rather than board feet for conversions
Conversion factors adjust seasonally and with regard to species
Understanding weight scaling factors, specifically moisture loss
J. Saralecos, University of Idaho, 2013
J. Saralecos, University of Idaho, 2012
•British Columbia Ministry of Forests, Lands, and Natural Resource Operations Scaling Manual. 2011. Weight Scale Sampling. Crown Publication. Victoria, British Columbia, Canada 14-1-4-34. •Bauer, E., Hogan, R. 2006. Log Scaling in Idaho, Scaling and Marketing Private Timber. University of Idaho Cooperative Extension •Fonseca, Matthew A. 2005. The Measurement of 1 Roundwood: Methodologies and Conversion Ratios. Wallingford, UK: CABI Pub.269p. •Bowyer, J. L., Shmulsky, R., and Haygreen, J. G. 2007. Forest Products and Wood Science: An Introduction. Blackwell Pub. Ames, Iowa. 558p. •Saralecos, J.D., Keefe, R.F., Brooks, R.H., Tinkham, W.T., Smith, A.M.S., and Johnson, L.J. In Review. Effects of harvesting systems and bole moisture loss on weight scaling of Douglas-fir sawlogs (Pseudotsuga menziesii). Forests.
Citations and Acknowledgements
Questions?
