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The aim of this study was to identify suitable locations for solar kilns in Vientiane, the capital of Laos, based on geographical and climatic conditions and restricted areas. The criteria of the parameters, which were incorporated with Fuzzy membership functions, were used to create layers in the ArcGIS environment to draw maps of suitability. Climatic parameters, based on the Fuzzy method, were used to investigate the period of productive performance for solar kilns. The results showed a range of possible locations. The most suitable locations were in flat areas near roads. They were far from protected areas, rivers, and flood prone areas. The most productive performance period for operating solar kilns was from November until May.

Understanding the rate of drying of standing trees dried by using a solar kiln drying method could help in predicting the change of moisture content in the tree over a period of drying time. The purpose of this study was to observe the change of moisture content profile in a standing tree during drying. A standing Tectona grandis tree was selected for the experiment with a diameter at breast height of 29 cm in a mixed-species plantation. The tree was girdled with 20 cm width at 20cm above ground. For the experiment, the tree was wrapped in a transparent plastic sheet and a black plastic sheet was installed at the bottom with an angle of 39 °C facing Southwest to maximize solar radiation, with the method being modified from the solar kiln method, which is known as a greenhouse type, with 2 layers of plastic cover. The black and white sheets were placed on the inner side for insulation and for collecting heat from the sun’s radiation, while the outer layer was transparent, which allowed radiation to propagate unhindered in the black sheet. In this study, a sensor for temperature and relative humidity (DHT22) was attached inside the wrapped plastic and the data recorded every 6 min. The results showed that drying a standing teak tree from an initial average moisture content of 105 % to a constant point of 60 % took 80 days under the maximum of the collected temperature of 46 °C inside the wrapped plastic; this finding confirmed that the predicted model of recharge and discharge curve was likely accurate.

Timber cracking, drying stress residuals, and the change of moisture content profile were investigated during the drying of Tectona grandis boards in a conventional laboratory kiln. The study applied a technique that simulated solar kiln conditions using a conventional laboratory kiln to dry timber, based on Vientiane’s climatic conditions (Laos). The theoretical recharge and discharge model was used to generate the potential drying schedule for the Vientiane area; then the drying schedule was mimicked in a conventional laboratory kiln. Timber cracking and drying stress residual were monitored and measured using Image J software, and the change of moisture content profile was determined, based on the oven dry method. Measured moisture content data were compared with the theoretical drying model. The results showed that teak boards, of 25 mm thick, had no cracking. The drying stress residual was 0.8 ± 0.3 mm with the maximum of 1.53 mm. The initial average moisture content of 62% decreased to 12% within 16 d, while the case and core moisture contents reached 12% and 14%, respectively. The drying model described the changes of moisture content profile during drying, with a maximal error of 5%.

The objective of this study was to investigate the most influenced levels of pressure and length of time on modulus of rupture (MOR) and modulus of elasticity (MOE) of teak laminated veneer lumber (LVL). Teak LVL was taken from the Faculty of Forestry’s forest plantation in Vientiane, Laos. The peeled veneer’s thickness was 2.3 mm. The veneer was air-dried until the moisture content reached the range of 6 to 10 %. Teak LVL panels were assembled from 9-ply panels of veneer using PL116- Liquid phenol-formaldehyde resin adhesive. The temperature was at 120 °C at 3 different pressure levels i.e., 1.5, 2 and 2.5 MPa and levels of time i.e. 9, 11 and 13 min. The experiment was conducted based on ISO16978. Intron Machine Model 5569 was used for the bending test of LVL with a dimension of 20×20×360 mm3. The bending test results on teak LVL showed significantly different MOR and MOE based on length of time and pressure levels of pressing.