Mersawa Wood: A Comprehensive Guide

 

Introduction

Mersawa is the Standard Malaysian Name for the wood of Anisoptera species, part of the Dipterocarpaceae family. Common vernacular names include kijal (Terengganu), loh (Pahang), medang sawa (Peninsular Malaysia), mersawa (Peninsular Malaysia and Sarawak), pengiran (Sabah), rengkong (Pahang), sanai (Peninsular Malaysia), and terbak (Kedah, Perlis, Kelantan). Major species include A. costata, A. curtisii, A. grossivenia, A. laevis, A. marginata, A. megistocarpa, and A. scaphula. The sapwood is not distinctly different from the heartwood, which ranges from light to dark yellow and darkens over time upon exposure.

 

Other names for Mersawa:

– Brunei: Mersawa

– Cambodia: Phdiek, Trabak, Ven ven

– Indonesia: Ketimpun, Masegar, Mersawa, Mersawa daun lebar

– Laos: Bak, Mai Bak

– Myanmar: Boilam, Kaban, Kaban thangyin, Kaunghmu

– Papua New Guinea: Garawa

– Philippines: Afu, Dagang, Dagum, Palosapis

– Thailand: Kabak, Krabak, Kra-Bark, Pik, Tabak

 

 Density

Mersawa is classified as a Light Hardwood, with a density ranging from 515-735 kg/m³ when air-dried.

 

 Natural Durability

Mersawa wood is moderately durable under exposed conditions. In a test conducted by the Forest Research Institute Malaysia (FRIM), untreated specimens lasted about 5 years. The wood is highly susceptible to fungal attacks. However, treated specimens of A. laevis with diesel/fuel mixtures demonstrated improved durability, with no signs of degradation after 2 years.

 

 Preservative Treatment

Mersawa wood is generally difficult to treat with preservatives.

 

 Texture and Grain

The texture of Mersawa wood is moderately coarse but even. The grain is typically interlocked, ranging from shallow to deeply interlocked and sometimes slightly spiral.

 

 Strength Properties

Mersawa falls into Strength Group C (Engku, 1988) or SG 6 (MS 544: Part 2: 2001).

 

| Species       | Modulus of Elasticity (MPa) | Modulus of Rupture (MPa) | Compression Parallel to Grain (MPa) | Compression Perpendicular to Grain (MPa) | Shear Strength (MPa) |

|——————|———————————|——————————|—————————————–|———————————————-|—————————|

| A. laevis    | 9,200                           | 49                           | 26                                      | 5.65                                        | 7.4                       |

| A. marginata | 12,600                          | 54                           | 28.9                                    | 5.52                                        | 7.1                       |

 

 Machining Properties

Mersawa wood is difficult to resaw and cross-cut due to the presence of silica, which dulls cutting tools. While it is challenging to plane, the final surface is smooth.

 

| Species       | Condition | Sawing | Planing | Boring | Turning |

|——————|—————|————|————-|————|————-|

| A. laevis    | Green         | Difficult  | Smooth      | Easy       | Moderately smooth |

|                  | Air-dry       | Difficult  | Smooth      | Rough      | Smooth        |

| A. marginata | Green         | Difficult  | Smooth      | Easy       | Moderately smooth |

|                  | Air-dry       | Difficult  | Smooth      | Rough      | Smooth        |

 

 Nailing Property

Nailing properties of Mersawa wood are rated as good.

 

 Air Drying

Mersawa wood dries very slowly with minor degrades. Minor cupping, bowing, and surface-checking are observed. 13 mm thick boards take 6 months to air dry, while 25 mm and 38 mm thick boards take 7.5 months and 9 months, respectively.

 

 Kiln-Drying

Kiln Schedule E is recommended for drying Mersawa wood. The timber dries slowly and retains high moisture content in the core. 25 mm thick boards take approximately 16-17 days to kiln-dry from 50% to 10% moisture content.

 

| Moisture Content (%) | Temperature (Dry Bulb) | Temperature (Wet Bulb) | Relative Humidity (%) |

|————————–|—————————-|—————————-|—————————|

| Green                    | 120°F (48.5°C)             | 115°F (46.0°C)             | 85%                       |

| 60                       | 120°F (48.5°C)             | 113°F (45.0°C)             | 80%                       |

| 40                       | 125°F (51.5°C)             | 116°F (46.5°C)             | 75%                       |

| 30                       | 130°F (54.5°C)             | 117°F (47.0°C)             | 65%                       |

| 25                       | 140°F (60.0°C)             | 120°F (48.5°C)             | 55%                       |

| 20                       | 155°F (68.0°C)             | 127°F (53.0°C)             | 45%                       |

| 10                       | 170°F (76.5°C)             | 136°F (58.0°C)             | 40%                       |

 

 Shrinkage

Mersawa wood has high shrinkage rates: 1.4% radial shrinkage and 3.5% tangential shrinkage.

 

 Defects

Mersawa is generally free from defects. However, some logs may contain spongy heart, and the sapwood is prone to ambrosia beetle attacks if left untreated in the forest after felling.

 

 Uses

Mersawa wood is highly regarded for plywood production and is suitable for a variety of applications, including:

– Light construction

– Door and window frames

– Posts, beams, and joists

– Furniture and pallets (expendable type)

– Packing boxes and crates

– Joinery and cabinet making

– Flooring

– Staircases (newel, sprandrel framing, tread, bullnose, round end, winder)

– Tool handles (non-impact)

– Disposable chopsticks