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Laminated mahogany and teak wood as construction materials for fishing vessels

The significant increase of Teak wood price causes the high price of fishing vessels made from intact Teak wood so that it is necessary to replace the Teak wood as the main material in fishing vessels. The traditional construction of fishing vessels has negative impact such as decreasing quality of the material due to heat treatment of wood, so that laminated wood technology with cold treatment is one solution to maintain and strengthen wood material. Mahogany wood is one of the woods that can be used as an alternative material for fishing vessels according to the Indonesian Classification Bureau, but some people assume that Mahogany is not suitable as an alternative for Teak wood due to differences in the durability of wood in seawater, so the research will be conducted on lamination of Mahogany and Teak as a material to build fishing vessel. This study carried out tensile and bending tests in accordance with ASTM standards for laminated material. Based on the results of test, the laminated material of Mahogany and Teak has an average tensile strength of 96.56 MPa, bending strength of 72.38 MPa and specific gravity of 0.82 gr/cm2. According to the regulations of the Indonesian Classification Bureau the laminate material of Mahogany and Teak meets minimum tensile strength and bending strength, equivalent with Strength Group II-III and can be used for the entire construction section of the fishing vessel. From the economic aspect it is estimated that the cost to build a 3 GT fishing vessel around IDR 44,927,656 (USD 3,160).


Introduction
Currently, the manufacturing of wooden fishing vessels still using solid Teak wood as raw materials. Teak wood is more expensive than the other woods that are used in boat building [1]. While in Indonesia there are various types of wood that are more abundant and cheaper than Teak wood, one of which is Mahogany wood [2].
According to Biro Klasifikasi Indonesia (BKI), It is allowed to use mahogany as a material for wooden ship construction. Mahogany wood is classified as Strength Group II-III. A whole part of Mahogany cannot be used for the entire construction of the wooden boat because the Durability Group is only a Durability Group III so that the solid Mahogany is only allowed to be used for constructions that not always interact with seawater [3]. Although BKI allowed using mahogany as raw material of wooden boat, the use of mahogany is not as much as Teak in Indonesia due to doubts by producers and consumers about the strength and durability of mahogany wood.
Mahogany wood has disadvantages, those are easy to experience deformation and shrinkage. The disadvantages can be overcome by the lamination method that has been done by some researches. With the use of epoxy resins, Mahogany lamination can maintain the shape of the hull and gain strength up to the equivalent of Strength Group I wood.
The last research proved that Mahogany lamination using epoxy had 115 MPa of the tensile strength, while the tensile strength of solid Mahogany is only 90.83 MPa and the Teak wood only 97.1 MPa [4]. To perfect the research, it is felt necessary to provide additional reinforcement to the construction made of Mahogany wood with wood which has proven to be stronger and more durable than Mahogany. Teak wood is wood that has a Strength Group I and Durability Group 1 and is expected to increase the durability of Mahogany lamination by making Teak wood as the outermost coating of Mahogany lamination material because the durability of Teak wood has been proven to be good for parts of construction that come in direct contact with seawater [5]. Therefore, it is necessary to conduct a research by adding a layer of Teak wood on Mahogany wood laminate.

Methodology
This research is motivated by the use of alternative wood substitutes for solid Teak and the application of lamination technology where the material chosen for research is Mahogany and Teak Wood. The study begins with the formulation of the problem regarding the method of making ships with these materials as well as technical analysis and economic analysis. After that, collecting literature related to problems and problem solving in research and surveys to obtain information about the current conditions in the construction of fishing vessels made from whole wood. Material testing is carried out to get the results of bending strength and tensile strength which will be used to consider the feasibility of the material in accordance with BKI [6]. The results of the material testing are used for construction calculations on the Mahogany 3GT laminated vessel. After testing and surveying, prototyping is carried out to obtain comparative data on the production process between the shipbuilding method with lamination technology and the shipbuilding method using solid wood [7]. From prototype shipbuilding also obtained data on shipbuilding productivity with lamination technology and costs related to the construction of laminated vessels which will be used as calculation factors in the economic analysis of the construction of Mahogany and Teak laminated fishing vessel 3 GT.

Material Test Result
From the results of tensile tests that have been carried out on the test specimens, the average elongation and Fault values will be shown, as shown in Table 1. The test results of Mahogany wood laminated material with Teak with aligned fiber direction arrangement obtained maximum bending value until the test specimen is broken [11]. Specimen 1 (TK 1) withstand a bending load of 1.4 kN. Specimen 2 (TK 2) holds a bending load of 1.6 kN. Specimen 3 (TK 3) holds the bending load 1.5 kN. Specimen 4 (TK 4) holds a bending load of 1.4 kN, and Specimen 5 (TK 5) holds a bending load of 1.4 kN.

Mechanical Properties of Tensile Test
From the tensile test results, the mechanical properties of Mahogany and Teak wood laminates can be calculated. From these calculations, the stress, MoE and Strain values obtained from the results of the tensile testing have been carried out. Details of the mechanical properties' calculation of Mahogany and Teak laminates can be seen in Table 3. According to the 2013 BKI regulation on "Rules for Small Vessels up to 24 m" which stipulates the permitted stress of plywood or laminate material, it states that the laminate to be used as construction material must have a minimum tensile strength value of 42,169 MPa [12]. Meanwhile, according to

Mechanical Properties of Bending Strength
From the results of bending testing can be calculated and obtained deflection values, bending strength and MoE from bending test data results for laminated Mahogany and Teak wood. At the time of conducting the bending test to measure deflection, it requires sufficient precision due to the necessity to observe deflection based on the sound of specimen cracks. For details on the calculation of bending test results can be seen in Table 4.  Figure 2. Specimen's bending strengthFigure 2.

Wood strength group and durability group
In BKI Regulation Volume VI of 2013 concerning "Rules for Small Vessels up to 24 m" wood material that is allowed to be used as shipbuilding material is material with a minimum of Strength Group III and Durability Group III. For Strength Group I more than 650 kg/mm 2 or more than 63.74MPa with a minimum specific gravity more than equal to 0.9gr/cm 3 , Strength Group II 450kg/mm 2 up to 650 kg/mm 2 or equivalent to 44.13-63.74 MPa with specific gravity between 0.6-0.9gr/cm 3 . Strength Group III 300 kg/mm 2 up to 450 kg/mm 2 or equivalent to 29.42 MPa -44. 13 MPa with a specific gravity of 0.4-0.6gr/cm 3 . Mahogany and Teak lamination material has an average tensile strength of 96.56 MPa with a specific gravity of 0.82 gr/cm 3 so that although it has a tensile strength equivalent to Strength Group I woods, in terms of its specific weight equivalent to Strength Group II wood, Mahogany and Teak wood lamination material equivalent to Strength Group II Wood. For durability group of laminated material According to BKI is durability group which is owned by wood with the lowest durability group namely Mahogany wood so that this material has Durability Group III.

Allowed use for construction
In BKI Regulation Volume VI of 2013 concerning "Rules for Small Vessels up to 24 m" the ability to use materials for each construction part has been determined based on the specific gravity of the material [13]. Because Mahogany and Teak laminated material have a specific gravity of 0.82 gr/mm 3 , this material is allowed to be used as construction material for all parts of the ship. For details of the permissibility of using Mahogany wood lamination material can be seen in Table 5.

Scantling For 3 GT Fishing Vessel
The calculation of the construction size was obtained based on the 2013 Biro Klasifikasi Indonesia (BKI) Volume VI regulations on "Rules for Small Vessels up to 24 m" [13]. The calculation is done based on Section 1 D about cold-molded in BKI Volume VII 2013. On the results of the determination of the construction of laminated wooden vessels. The results of the calculation of the size of the construction of Mahogany and Teak laminated teams of 3 GT can be seen in Table 6.

Economic Analysis
The main material costs calculated in the construction of Mahogany and Teak Laminated Fishing vessel 3 GT are the costs of wood materials, the cost of the need for epoxy resin glue, and materials other than the main material of laminated wood used on ships. Raw material costs are calculated to determine the Prime Cost:

Wooden material cost
The price of wood used in the construction of Mahogany and Teak laminated fishing vessel 3GT can be seen in Table 8

Epoxy resin material cost
Epoxy resin glue used in the construction of Mahogany and Teak laminated Fishing vessel in this study uses Propan EWA-135 which has a price of IDR 110,000.00. Coverage area is an area that can be fulfilled by 1 kg of epoxy resin glue based on the amount used in the construction of Mahogany and Teak laminated fishing vessel which is 0.5 m 2 /kg. The cost of glue per m 2 is calculated based on the weight of glue used in the area of square meters gluing obtained at 0.5kg/m 2 . Detail calculation of glue requirements can be seen in Table 9.

Fastener material cost
In addition to wood and epoxy resin, other materials are needed as fasteners which serve to strengthen the connections in the ship's modules. These materials are nails, studs, screws, bolts, and O-rings. For details on the cost of fastener raw materials for making Mahogany and Teak laminated fishing vessel 3 GT can be seen in Table 10 with a total cost of IDR 1,348,500.

Coating cost
Painting of Mahogany and Teak laminated fishing vessel uses 3 types of coatings namely primary coat, topcoat, and anti-fouling. Painting is assumed to only be carried out on the outer layer of the hull [14]. The cost of paint at the primary coating stage is IDR 294,666.67, the anti-fouling fee is IDR 111,822.22, and the cost of top coating is IDR 835,377.78. The total cost of painting the Mahogany and Teak laminated fishing vessel 3 GT is IDR 835,377.78. Detailed calculation of painting needs in the construction of Mahogany and Teak laminated fishing vessel 3GT can be seen in Table 11.

Variable cost
Variable costs are costs incurred in every ship construction outside the cost of basic materials. Items included in the variable costs are consumables and related services needed for the construction of Mahogany laminated fishing vessels and 3 GT teak. Details of variable costs can be seen in Table 12.

Fixed cost
Fixed costs are costs used to procure materials that do not change in price due to production processes such as machinery and workshop facilities. In the construction of 3 GT laminated fishing vessel and Mahogany wood, machines and equipment as production support are needed which are included in fixed costs. For details on fixed costs, see Table 13 .

Prime cost
From the price calculation that has been done in Table 8 to Table 12, the cost of building Mahogany and Teak laminated fishes can be calculated. Calculation of total costs for Mahogany construction and Teak laminated fishing vessel can be seen in Table 15. The total construction of Mahogany and Teak laminated fishing vessel is IDR 40,843,323.55. Mahogany and Teak laminated fish boat 3GT has a total construction cost of IDR 40,843,323.55. To estimate the selling price of ships in the market, the author determines the profit of selling ships at 15% of the total construction cost. With a sales profit of 15% of the cost of production, a profit of IDR 4,084,332.35. Estimated sales price per ship for Mahogany and Teak laminated fish boat is IDR 44,927,655.90. Calculation of the selling price of ships can be seen in Table 16.

Conclusions
Based on the technical analysis and economic analysis explained in the previous chapter, the following conclusions are obtained: 1. Based on the prototype development of the 3 GT laminated fishing vessel that has been built, the technical analysis and economic analysis that has been carried out in this research, shows that Mahogany and Teak wood lamination material can be used to build traditional 3 GT fishing vessels using the Cold Press Planking Method.