Pelawan
(Northern Box)
INTRODUCTION
The Standard
Malaysian Name as well as the ASEAN Standard Name for the timber of Tristaniopsis spp. (Myrtaceae). Vernacular names applied include keruntum (Peninsular Malaysia), malaban (Sarawak), melaban
(Sarawak), pelawan-pelawan (Sabah), seluchor (Peninsular Malaysia), selunsor
(Sarawak) and selunsor puteh
(Sarawak). Major species include T. merguensis, T.
obovata and T. whiteana.
The sapwood is pink-brown or red-brown and is lighter in colour than the heartwood,
which is pink-brown, red-brown or purple-brown, sometimes with a grey tinge.
Also known
as Brush box and Yellow panda (Australia); Rong leang (Cambodia); Balaban, Pelawan, Pelawan Merah, Pelawan Talang, Radja, Tabi and Wawako (Indonesia); Duakyat (Myanmar); Papua New Guinea swamp box
and Swamp mahogany (Papua New Guinea); Malabayabas,
Taba and Tiga
(Philippines); and Tamsao-nu (Thailand).
DENSITY
The timber
is hard to very hard and heavy to very heavy with a density of 915-1,250 kg/m3
air dry.
NATURAL
DURABILITY
The timber
is reputed to be very durable. Related species have been tested in other
countries and found to be very durable under all conditions and even resistant
to termite and marine borer attacks (Wong, 1976).
TEXTURE
Texture is
rather fine and even, with interlocked, sometimes wavy grain.
STRENGTH PROPERTIES
The timber
falls into Strength Group A (Abdul, 1985).
Strength Properties of Pelawan
(T. obovata)
|
Test Condition |
Modulus of Elasticity(MPa) |
Modulus of Rupture(MPa) |
Compression parallel to grain (MPa) |
Compression perpendicular to grain (MPa) |
Shear Strength(MPa) |
|
Green |
14,167 |
111.0 |
51.7 |
- |
12.4 |
|
Air dry |
20,732 |
170.0 |
72.6 |
- |
18.4 |
MACHINING PROPERTIES
The timber
is reported to be difficult to saw but can be finished to a very smooth
surface.
AIR DRYING
The timber
seasons moderately slowly. 40 mm thick boards take approximately 5 months to
air dry. Drying defects are not particularly serious and only minor defects
such as light end-checking, splitting, etc., have been recorded.
KILN-DRYING
Schedule D is recommended. The timber is liable to
cupping and end-checking. 25 mm thick boards take approximately 9 days to dry.
Kiln Schedule D
|
Moisture
content (%) |
Temperature (Dry Bulb) |
Temperature (Wet Bulb) |
Relative Humidity (%) (approximately) |
||
|
o F |
o C |
o F |
o C |
||
|
Green |
105 |
40.5 |
101 |
38.0 |
85 |
|
60 |
105 |
40.5 |
99 |
37.0 |
80 |
|
40 |
105 |
40.5 |
96 |
35.5 |
70 |
|
35 |
110 |
43.5 |
97 |
36.0 |
60 |
|
30 |
115 |
46.0 |
97 |
36.0 |
50 |
|
25 |
125 |
51.5 |
101 |
38.0 |
40 |
|
20 |
140 |
60.0 |
105 |
40.5 |
30 |
|
15 |
150 |
65.5 |
112 |
44.5 |
30 |
SHRINKAGE
Radial
shrinkage averages 2.6%, while tangential shrinkage averages 3.8%.
USES
The timber
is suitable for all heavy constructional works, posts, beams, joists, rafters,
tools handles (impact), heavy duty furniture, vehicle bodies (framework,
planking and floor boards), door and window frames and sills, columns
(heavy duty), staircase (carriage, newel, riser, stringer, tread, bullnose, round end and winder), boat framing and other
marine construction. It should also be suitable for heavy-duty flooring.
REFERENCES