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GENERAL AND TECHNICAL DESCRIPTION OF KAUNGH MU (MERSAWA)
DISTRIBUTION
Very widely scattered, being found growing in peat swamp forests, low flat land and on hills.
Name Kaungh Mu
Family Anisoptera scaphula
Common Names
Myanmar Kaungh Mu
India Kaungh Mu/ Mersawa
Malaysia Mersawa
Thailand Krabak, Pik
Philippines Palosapis
GENERAL DESCRIPTION
Sapwood is not well-defined. Heartwood is light to dark yellow and darkens on exposure.
Grain is shallowly to deeply interlocked.
Texture is moderately coarse and even.
Vessels are with simple perforations, medium-sized or moderately large, generally moderately few in
number, exclusively solitary or predominantly solitary, with a few radial or oblique pairs that are diffused,
but with a tendency to align in short oblique lines.
Wood parenchyma is of both the apotracheal and paratracheal types; apotracheal type in scattered groups,
locally joined to produce short tangential lines and also found associated with the vertical resin canals
which are both diffused as well as in concentric series; paratracheal parenchyma is vasicentric, forming
narrow borders to the vessels.
Rays are of two distinct sizes; broader rays are medium-sized or moderately broad and distinct to the
naked eye on the cross-section and conspicuous on the radial surface, producing a vague silver figure; the
finer rays are interspersed among the broader rays.
PHYSICAL PROPERTIES
Air-Dry Density 515 - 735 kg/m3
Radial Shrinkage 1.40%
Tangential Shrinkage 3.2 to 3.8 %
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SEASONING & SHRINKAGE
Seasoning characteristics are based on test results using test boards placed on 25 mm stickers. The test
boards were stacked in open-sided sheds and were protected from rain and direct sunlight. Shrinkage data
are given for both the radial and the tangential directions. The data expressed in percentage of the width in
the green condition, are based on measurements from the green to the air-dry condition (15% m.c.).
MECHANICAL PROPERTIES
The mechanical properties have been determined using the test procedure described in ASTM designation:
developed by the American Society for Testing Materials.
Strength group
Four strength groups are used, viz., strength groups A, B, C and D. The earlier grouping method (Burgess,
1958) based solely on compression strength parallel to grain is given in the table below.
Strength Grouping Table
Strength Group Compression strength parallel to grain
A greater than 55.2; extremely strong
B 41.4 - 55.2; very strong
C 27.6 - 41.4; moderately strong
D less than 27.6; weakest
A refinement to the earlier method took into consideration the basic and grade stresses (Engku Abdul
Rahman, 1960). Some timbers have been grouped using this method. For the remaining timbers, the earlier
grouping has been used.
Static bending
Data on the Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) have been obtained from
published test data (Lee et al, 1979). The mean values are given in the air-dried condition (unless
otherwise indicated). If a range is given, it shows the lowest and highest for the timber group.
Compression strength
Data on compression strength perpendicular to grain and compression strength parallel to grain have been
obtained from published test data (Lee et al, 1979). If a range is given, it shows the lowest and highest
values found for each timber.
Shear strength
Data on shear strength have been obtained from published test data (Lee et al, 1979). If a range is given, it
shows the lowest and highest values found for each timber.
DURABILITY -Moderately durable
Durability refers to the natural durability of the heartwood of the timber. It has been found useful and
convenient to classify durability into four groups, as shown in the table below.
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Natural Durability Grouping
Group Number of years
Very durable exceeding 10 years
Durable 5 - 10 years
Moderately durable 2 - 5 years
Non-durable 0 - 2 year
The placement of any timber in any of these four groups is based on its performance in 'graveyard' testing.
This method of testing entails the monitoring of test-sticks measuring 50 x 50 x 600 mm buried in test
grounds. The number of years that the test-sticks can last is the basis for the grouping.
Great care should be exercised when considering durability. It must be emphasized that the number of
years, shown in the Table above, is relevant only to the test-sticks, which measure only 50 x 50 mm in
cross-section, and that the tests have been conducted under extremely drastic environmental conditions
where the test-sticks are subjected not only to weather extremities but also to attack by a very wide range of
wood attacking organisms.
The number of years shown above is therefore only a yardstick for the grouping exercise and the actual
service life of the timber can be expected to be much better under the more docile conditions for common
usage, especially in temperate countries where climatic and other conditions are less conducive to the
activity of biodeteriorating organisms.
TREATABILITY-Difficult
The evaluation of treatability is based on the rate of absorption of preservative when test specimens of
standard dimensions are subjected to an open-tank treatment using a mixture of 50% creosote and 50%
diesel oil heated to a temperature of 87°C in 2 1/2 hours and maintained at this temperature for 1 hour
before cooling to room temperature over a period of 16 hours. It has been found convenient to classify
treatability into seven groups as shown in the Treatability Grouping below.
Treatability Grouping
Grouping Chemical Absorption Range
Extremely Easy Greater than 320 kg/m3
Very easy 130 - 190 kg/m3
Average 95 - 130 kg/m3
Moderately Difficult 65 - 95 kg/m3
Difficult 30 - 65 kg/m3
Very Difficult less than 30 kg/m3
Working Properties
Planing: Difficult
Finish: Smooth
Boring: Easy
Finish: Rough
Turning: Easy
Finish: Smooth
Nailing: Good
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The working properties of the timbers have been obtained from published data (Lopez, 1978) and (Lee &
Lopez, 1980). For each of the three operations mentioned below, the degree of difficulty in the machining
process is cited as well as the quality of the finish obtained. It must however be pointed out that for the
purpose of direct comparison, the test specimens were subjected to a fixed set of machining parameters
which will not necessarily be the optimum set for any particular timber, especially in respect of the quality
of the finish. Manipulation of parameters such as feed speed, knife angle etc. can result in an appreciable
improvement in the quality of finish.
Planing
Test results were obtained from specimens planed with surface thicknesses. The cutter head speed was set
at 400 r.p.m. and a feed speed of 6m/min. was used. The degree of difficulty in planing is classified into six
categories, viz., Easy; fairly easy; moderately easy; slightly difficult; Difficult; and Very difficult. The
quality of finish of the planed surface is classified into four grades, viz., Smooth; Moderately Smooth;
Rough; and Woolly.
Boring
Test results were obtained from specimens bored with a machine-borer at a speed of 700 r.p.m. Boring bits
used were a 25 mm wing boring bit, a 25 mm machine dowel bit and a 19 mm machine twist drill taper
shank.
The degree of difficulty in boring is classified into five categories, viz., Easy; moderately easy; slightly
difficult; Difficult; and Very difficult.
The quality of finish is classified into six grades, viz., Very smooth; Smooth; fairly smooth; slightly rough;
Rough; and Tearing of grain.
Turning
Test results were obtained from specimens turned with a woodturning lathe. Two head stock speeds were
used, viz., 500 r.p.m. (slow) and 1150 r.p.m. (fast). The following chisel type turning tools were used
Skew type- 6 mm, 12 mm, and 25 mm
Gauge type- 12 mm, 19 mm, and 25 mm
Spear point type- 6 mm, and 12 mm
Flat nose type- from 3 mm, to 25 mm
Round nose type- 6 mm, and 12 mm
The degree of difficulty in turning is classified into five categories, viz., Easy; moderately easy; slightly
difficult; Difficult; and Very difficult. The quality of finish is classified into four grades, viz., Smooth;
moderately smooth; slightly rough and Rough.
Nailing
Test results were obtained from specimens hand nailed using common wire nails spaced at fixed intervals.
An ordinary carpenter's hammer was used and no pre-boring was carried out. Resistance to splitting is the
criteria used to assess the nailing properties. Four grades are used, viz., Excellent; Good; Poor; and Very
poor.
USES
Suitable for light construction, door and window frames, flooring, ceilings, weather boards, packing cases,
crates, boxes and plywood.
