lec 5 preparation, defects & seasoning of woodlec2
Post on 10-Dec-2015
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Logging
1. Cutting of the tree.
2. Skidding – when logs are moved to an assembly area loaded to transport equipment then carried out of the forest to the sawmill.
3. Bucking – the process of sawing into smaller pieces.
The harvesting of the tree
crops consisting of a
sequence of operations
such as:
Previously, all felling and bucking operations
were done by the use of axe, saw, and
wedges. Lately, however, the felling of
trees were done using motor powered
chain saw.
Terminologies
Skidded – when the log is dragged and
carried down to an assembly area.
Yarded – when logs are delivered through
the cable or a helium filled balloon.
Lumbering – the operation performed in
preparing wood for commercial purposes.
Sawing – cutting logs.
Two Methods of Log Sawing
Employed are:
1.The Plain or
Bastard sawing
- is by cutting the logs
entirely through the
diameter with a parallel
chord tangential to the
annual rings.
2. The Quarter of Rift sawing
a.Radial method
b.Tangential
method
c.Quarter
tangential
d.Combined Radial
and Tangential
Main
Defects in Wood
- Irregularities found in wood are considered
as defects. The most common defects are:
A. Abnormal Growth
B. Due to Deterioration
A. Abnormal Growth are identified as:
1.Heart Shakes –
radial cracks
originating at the
heart of the logs.
2. Wind Shakes or
Cup shakes –
cracks or breaks
across the annual
rings of timber.
3. Star Shakes –
composed of several
heart shakes in a star-
like manner.
4. Knots – usually occurs
at the starting point of
a limb or branch of the
wood.
B. Due to deterioration caused by:
1.Dry-Rot – the
presence of
moisture in
seasoned
wood caused
by fungi.
Seasoning of Wood
Seasoning – drying of lumber.
The water contained in a freshly cut
wood constitute about one third to more
than two thirds of its weight. The removalof much of this
moisture is
accomplished by way
of seasoning also
known a conditioning
or curing.
Two Methods of Seasoning Wood
1. The Natural or Air Seasoning
a. Lumber is piled
vertically outdoor
inclined at about
10 degrees.
b. Lumber is piled
in a well-
ventilated shed.
2. The Artificial Seasoning
- is the process adopted
for quick drying of wood.
Under this method,
lumber are stacked inside
a drying kiln and then
subjected to steam and
hot air under pressure.
Wood that undergone this
process are considered inferior
in quality compared to those
that were dried by natural or air
seasoning process.
The Artificial Seasoning Methods
Employed are:
1.Forced Air Drying – fans are used
to booster the circulation of air a
preparatory process to kiln drying.
2. Kiln Drying – the lumber is dried in a
specially built chamber wherein
temperature and humidity as well as
the circulation of air is under control.
3. Radio Frequency Dielectric Drying – a
very fast method of drying lumber
using a radio frequency dielectric heat.
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