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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


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