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Preservative absorption response of planks of Anogeissus acuminata for plank-built catamarans
2002 - IRG/WP 02-40245
Due to shortage of timber coupled with other compelling factors, traditional fishermen along the east coast of India, especially of Andhra Pradesh, of late, are departing from conventional log type wooden catamarans. Instead, they are fabricating catamarans out of timber planks of hard woods and utilizing thermocol for buoyancy. Mostly, locally available timber of a Combretaceae species, Anogeissus acuminata (Yon) is used to fabricate these plank-built catamarans. Since these catamarans are also built with untreated timber, there is every need to extend wood preservation technology to these craft also so as to achieve enhanced service life and conserve the resources. Therefore, the Institute of Wood Science and Technology took up treatment of timber meant for five such craft with copper-chrome-arsenic (CCA). Thirteen different logs were procured and converted into planks and batons of suitable sizes, debarked, cleaned and air dried under shade. While the length of the planks ranged from 0.81 to 6.53 m, the width varied from 16 to 44 cm. After sufficient seasoning, the material was pressure treated with 6% CCA by full cell method as per IS: 401 (1982). Chemical retentions were computed from the weight gained by the individual planks and sets of 20 batons immediately after treatment. The preservative absorption in the planks ranged from 13.05 to 69.80 kg/m3 averaging at 25.90 kg/m3 and that in the batons averaged at 32 kg/m3. The quantity of CCA absorbed by the planks was analyzed with reference to their length, width, thickness and volume. Planks when categorized to different length and volume groups exhibited clear difference in the intake of chemical by them but when categorized into different width and thickness classes showed not much variation. All the treated planks and batons after air drying in shade for 15 days were fabricated into five catamarans. Thus, though the planks of A. acuminata are either very long or very wide, they showed a positive response to CCA treatment by absorbing reasonably good quantities of preservative. Similarly, on fabrication of the catamarans, an average retention of 21.79 to 25.43 kg/m3 of CCA per craft could be achieved. These values fall into the recommended preservative absorption range of 16 to 32 kg/m3 (IS: 401, 1982) for marine structures.
V Kuppusamy, M V Rao, M Balaji, K Rao


Introduction of plank-built catamarans along the north coast of Andhra Pradesh, India – A development of recent origin
2003 - IRG/WP 03-10483
Hitherto, the most versatile fishing craft of the poor traditional Indian fishermen - the catamaran is made of solid timber logs of a few selected species of broad-leaved softwoods. Of late, the fishermen find it difficult to get these conventional varieties of timber chiefly because of three reasons, a) scarcity of commodity, b) prohibitive costs and c) competition from match and veneer industries. As the state of affairs is turning more and more indocile, the poor traditional fisherman is compelled to look for alternative ways to sustain his dear occupation and trade. As an outcome of such fervent desire, the fishermen in the north east coast of Andhra Pradesh initiated building up catamarans purely from the wooden planks without sacrificing much of the original shape, convenience and carrying capacity. This paper is intended to bring to light the design of such plank-built catamarans and their advantages.
M V Rao, K S Rao, M Balaji, V Kuppusamy


Durability of Anogeissus acuminata timber used for plank-built catamarans
2005 - IRG/WP 05-10551
Catamaran, the most versatile traditional fishing craft used along the Indian coast is made hitherto of solid timber of a few selected species of broad-leaved soft woods. Due to scarcity coupled with high cost of these timbers, the craft, of late, are fabricated from the wooden planks of an indigenous hardwood species, namely, Anogeissus acuminata (Yon) belonging to the family Combretaceae. Information on the durability characteristic of Anogeissus acuminata in marine environment is lacking. Therefore, the property was assessed at Visakhapatnam harbour, East Coast of India. Test panels of the species were pressure treated with 6% solutions of copper chrome arsenic (CCA) and copper chrome boric (CCB) wood preservatives and the treated panels along with controls in five replications were put to marine exposure trials. The tests revealed that untreated panels of A. acuminata suffered extensive damage from the wood borers, especially teredinids and were rejected in 15 months. On the other hand, CCB treated panels had undergone only 10 to 20 % destruction during the same period while CCA treated panels remained free from borer attack. However, both categories of treated panels subsequently succumbed to intense borer damage. While CCB panels were destroyed in 21 months, CCA panels were rejected in 27 months.
M V Rao, M Balaji, V Kuppusamy, K S Rao


Leaching of CCA from Bombax ceiba catamarans in operation for 15 years
2002 - IRG/WP 02-50191
Core samples of wood at random were collected from all the timber pieces of each of the three catamarans made of CCA treated logs of Bombax ceiba put to continuous service for the last 15 years at the Lawson's Bay fishing village, Visakhapatnam. The samples were dried to constant weight, powdered, digested and analyzed for the residual salts of the preservative. The residual content of CCA was found to be 6.90, 6.24 and 7.43 kg/m3 in CAT I, II and III, respectively. The values for individual components of arsenic, copper and chrome were 0.24 to 0.34 kg/m3, 3.34 to 4.37 kg/m3 and 2.66 to 3.03 kg/m3, respectively. Making use of the initial absorptions of the preservative determined at the time of treatment and the residual contents estimated now, the leaching rates of CCA and it's components were calculated. While the annual leaching rate of CCA was observed to be 1.22 kg/m3 (CAT I), 0.81 kg/m3 (CAT II) and 0.83 kg/m3 (CAT III), at elemental level, it was found to be 0.05, 0.04 and 0.05 kg/m3 in the case of arsenic, 0.15, 0.10 and 0.09 kg/m3 in the case of copper and 0.20, 0.12 and 0.14 kg/m3 in the case of chromium for CAT I, II and III, respectively. The results thus indicate that while about 2/3rd the initial amount of CCA had been leached out of the catamarans during the last 15 years, still 1/3rd the amount is present in the logs. Thus, the preservative left out in the catamarans appears to be sufficient to offer protection to the craft for a good number of years to come.
V Kuppusamy, M Balaji, M V Rao, K S Rao


The present status of wooden catamarans of the Indian Coast
1997 - IRG/WP 97-10231
Catamarans (a.k.a. kattumarams) are the most widely used fishing craft in India, and hundreds of thousands of poor, traditional fishermen depend on these vessels for their livelihood that are almost made entirely of wood. In recent years, acute shortages and phenomenal increases in prices of timber species used in catamaran fabrication have been reported, causing great hardship to the user community. Further, the patterns of usage are based on age-old practices and not on scientific lines, resulting in significant waste of timber during fabrication and use. This paper, while highlighting the importance and benefit of usage of catamarans in the Indian context, stresses the need for introduction of steps to ameliorate the current losses, and outlines the various research and development efforts undertaken in this direction. Of special importance in this context is the on-going World Bank-aided program on catamarans, being handled at the Institute of Wood Science and Technology, Bangalore.
K S Rao