Utilization of treated wood, steel, fibreglass, ferrocement and aluminium in the construction of modern fishing boats and their comparative cost analysis
Item Type article
Authors Balasubramanyan, R.
Download date 03/10/2021 18:01:09
Link to Item http://hdl.handle.net/1834/33611 LIZ OF EATE OD, EGlASS, FERROCE E I E CO CTION F FISH I EIR CO E COST lYSIS.
R. RALASUBRAMANYAN Central Institute of Fisheries Technology Croft & Gear Division, Cochin-11.
Modern fishing boats have to be built not only on perfect Jines but also with sound and strong construction materials that will ensure a long lasting trouble free service commensurate with the heavy capital investment involved. Choice of construction materials for fishing boats need careful scrutiny as they have to perform too well under most aggressive environments- sea-water and marine atmosphere. A number of alternative boat-building materials are now available whose comparative merits and deme rits as well as comparative costs are brought out in this paper.
INTRODUCTION gress of construction of these vessels and the programme of fleet expansion have been The Fishing Industry in India today, considerably retarded due to shortage of has assumed a v~ry great economic impor the required constructional materials and tance and our fishing fleet comprising of due to their spiraling high costs. Owning boats of different types, shapes and sizes, of fishing fleet now warrants heavy capi represent the larg~st single collective in tal investment against uncertain returns. vestment on whose efficient performance The fishing industry ·in India to-day has depends the economy of millions of people reached a stage where it is in need of and the lives of an untold number of technically, economically and socially sound fisherman. Apart from the innumerous propositions to develop her fishing fleet indigenous fishing crafts spread out aU further with special reference to the pro along our Indian coast line, there are grammed exploitation of the fishery re nearly 8000 mechanised wooden fishing sources of the deeper waters. It is not boats and about 50 ·steel trawlers active only a sound design, proper size or type ly engaged to-day in the exploitation of of fishing vessel that is the need of the the marine fishery resources of India. hour but also what exactly is the choice Nearly 5000 wooden trawlers and 200 of material that is required for their steel trawlers are likely to be added to construction. The need for an efficient the existing fleet of fishing vessels in the boat to stand all the rigorous conditions near future. However, of late, the pro- of fishing in the open sea with a rna-
VoL X No 1 1973 33 'Balasulhamanyan: Utilization of treated mood, steel, fifheglass, (errocement and aluminium in tfre construction of medium fisf'ting boats and tfteir compa1·atiue analysis.
ximum economy in its working and main demerits in the overall technological cha tenance under the existing operational con racteristics of each material has to be ditions in India has to be fulfilled as analysed in greater details and the best much as possible in the light of the tra characteristics of that material selected, ditional construction materials available has to be taken to greater advantage be like wood and steel as also the modern fore the final construction is decided. materials like Aluminium-alloy, Fibreglass The present paper is an attempt in the Reinforced Plastics (FRP) and "Ferroce above lines wherein the salient characteris ment" (steel and cement). tics of newer construction materials are brought out in comparison with the weB Before a careful selection of the pro known wood and steel along with their com per material for the construction of the parative cost analysis (Table I, II, III & IV). fishing vessels is made, both merits and
TABLE I
Approximat cost Normal service ~life Area where in Timber species in fishing -boats. use. per ft3/m 3 in long form.
Untreated Teak 10 to 12 years Gujarat, Maharashtra. Rs 14 to 16/ (Tectona grandis) Rs 484 to 565/-
, " 10 to 12 years Andhra Pradesh Rs 15 to 18/ Rs 530 to 635/-
,, 10 to 12 years Kerala, Mysore, Rs 25 to 30/- Tamil Nadu. Rs 883 to 1059 (-
Kerala, Mysore, Untreated Aini Tamil Nadu, Rs 17 to 20/ 10 to 12 years (Artocarpus hirsuta) Pondicherry & Rs 600 to 705/- Laccadives.
Untreated Venteak (Lagerstroemia Lanceo Rs 7 to 8/ 10 to 12 yerrs Kerala, Tamil Nadu. Rs to _ lata) 296 3381 (C.I. F.T. Finding)
Seasoned and treated Untreated Rs 4 woods like mango Seasoning Rs 2 (Mangifera indica) A recommendation Treatment Rs 4 About 15 years. Haldu (Adina cardi for future use. Handing Rs 2 folia) Total Rs 12j-
(C.I.F.T. finding) Rs 424/ms
34 FISHERY TECHNOLOGY < t;;J 0 " t""' ~·~ ;s I'! TABLE COMPARATIVE COST OF BASIC RAW MATERIALS FOR BOAT CONSTRUCTION IN INDIA, 0'> :>< 2 ... -~l:J (Based on 1971 Price Level) (\) :i z Q 0 0" 1::::s :; Q (/) :; :;- .. ------·--~------~---~--~----~------Type of Specific Average hull Approximate cost per :::: " ("""' S.No. Remarks ~;:::' \0 hull gravity Thickness Ton 0 :.::..:. --....) ~ ..... w (/) "' 0 a.... .,_,._0 Considerable fluctuation in prices from region to ;s
regin and from species to species. ~ ,, o.::... P... Teak wood : Rs 15--30 per Cu.foot in rounds. (1) ...... Venteak wood; Rs " , ;s (1) Boat building timber: 7-3 ;::, Aini wood : Rs 17-22 " _<; 0.6-0.7 Rs S d o, ~·~ 400-1500/- " ;:;:, easone o~ without faste- Boat fastenings assorted: Treated Rs , ;;· Cj . 11" Man-: 12-13 , <0 0 mngs. ~ - 2f' 0 1 Wood Galvanized iron: go & Haldu 0'>-P... 0.9-0.95 with (37.5-62.5 mm) 0 Rs BOOO- 9000/- Price very much depands upon 0 the choice of me- (/) (/)..... - (1) fastenings. Copper/Brass: tal and surface coating: (1) 0 -- Rs 18,000-22,000/- Ordinary iron : Rs 2.50-3,50 ;:; per kg. ~:::- 0';> Galvanised iron ...... ;::.,g (Hot dip) Rs 7-8 :. S' . (/) Copper/Brass " Rs 18-22 , -"' Aluminized iron Rs 10/- , "0:;!--. ... (1) '1:l' ... Copper/Brass : Rs 18-22 p ... " ... 0 ;::, " - (1) Special · quolity high car ;· ::: Material· has restriced supply; very high (1) ;s(1) bon ship-building steel cost .... with retailers at 2 Steel 7.9 4-8 mm. 0 0 plates. (/)" ... Rs 2000 to 2300/- per ton. ""- ... Rs 1600-1700/~ ~ p ;:; p -::::0 - t:.:: :: (/) - .....~·;· :::: w v-. Contd/ ;:: w I:X:l Q'< I 2 5 6 a. .,_=--=~-~,..,..,·y·~·.,...~------~ .... t:l
;. "'<:: 'A'~glass chopped strand o• ..... '"' ~t:l mat as per B.S. 3496/ t'>l ;s l;l 1962. (") :::: Tbe superior materials like 'E' variety of glass 0 <.:::: ;::; .. 300 g/M~ [J> ;:: fibre and Epoxy resins are still costlier in ::-., 450 " India. ~ 600 ,, &~ Fibreglass 0 ~. 25,000/~Price in foreign marKets: r:s !:":' 3 reinforced 1.4~1.8 10~20 mm. 750 , Fibreglass • Rs 14000/ = per ton 0 "!;. plastics. 30 ends wo- ~a· Resin - Rs 4000/ ~ " - ;:! ven roving; ;:: Cost will increase considerably with the slight u Q Polyester resin bl- ~ increase in hull thikness. (0 ;:: ..... Rs 20,000/~ "' '"j II> ( Accelerater, Catalyst, .._,>:>...... "'i""l:l... "' Pigments etc) ;;:· \';) g~ Mild steel rods , 0'>0 (,) l:l,. Rs 1100-1200/-per ton p - ..... Cement: (Jl "'..... (I) Rs 200-240/- " !:) ~ Price with retailere at Rs 2000/- per ton. ;s - Galvanized iron pipe : P-..._ 3 ,_. II'' Steel and cement content has to be maintain .... 4 "2' ..... '-"' Rs 3500/- per tons ~"( Ferro (Q (I) 2.4-2,6 ed at 1:4 by weight; excessive cement plas ..... '.J::l 4 (18.75- Galvanized iron chicken cement '"' 37.50 mm) tering over the reinforcement should be -"' wire machine made we ('\ ·"'"' discouraged. 0 bbing of 20 SWG: ;;!--. 't:7 (I) Rs 6500-7000/- per ton p "'I "'p '"j0 .... <) Good quality river ..... (I> ":rj ~ :! {/) sand extra. (I) -::p :::: (") l"l"l 0 - id Marine quality Alumini ~ t:l >< :::: um -magnesium alloy pla Range of magnesium content in the alloy: !:) P ~ ;:: g Aluminium tes and extrusions similar 2 to 5% c l:l 5 2.5-2.7 4- gmm. c2'~ z -alloy to 5086, 5052 of U.S.A. Welding by metal Inert Gas or Tungsten Inert (I) = (I).... -.... ~ and 57S' E45S of Canada Gas and revtting with compatible alloys for best ;:s 0 ;::· Q at Rs. 12,500/-per ton. results. s >-< s TABLE III CoNPARATIVE cosT ESTIMATION OF A 57' OAL :X18 1 X 7'-3" (17.10m. :X5.40m. X 2.2m.) c:; t"" ~ FISHING TRAWLER MADE OUT OF DIFFERENT MATERIALS IN INDIA. ... p ;:l "' 0'0-= >< .... ""! (Approximate values + or - 10%) ~p "' 3 z Note - (1) Hull, deck and sup?r str~tctureinclusive. 0 () § 0\!;! Main engine, auxiliary deck fittings and fishing gear exclusive. ;:: p ..... ~;:: (2) Estimation exclusively based on cost of rmv materials and '"' ;:: .. Labour but not inclusive overheads and profits. \0 of ~~...... ---.J 0 .... w ;s;;:' N Normol life in _0- 1:>.... S.No. Trawler details Price range 0 tropical waters· ;s ;i 0 0 P..."""' Steel trawler with aluminium sup~rstructure All India Price ""!-"' 1 About 15 years ;::: ""! (Indig~n')m) Rs 5.50 L:tkhs (Ex.yard) "'0 -....."' "' P... ~ Rs 2.25 Lakhs in Gujerat area (Ex.yard) ~a 0 Rs 2.40 Lakhs in Andhra Pradesh (Ex. yard) 0 o-P... Wooden trawler (without hull sheathing) 0 " Rs 3.75 to 4.25 L:tkhs in Kerala, Mysore, p Madras & Pondicherry. About 10 to 12 "''"'""' (a) Conventional wooden trawler. -"'(1) years. 1:>-- Teak/ G.l. fastenings. ;:;: Rs 2.10 Lakhs (Ex.yard) p_,.,.... 2 .... (b) Cheaper version of C.I.F.T' Venteak Cost of hull protection for the W:Joden trawler: ,..,._.,0'0 (1)\CJ~"' sh~at'1ing 10 to 12 years and other treatd woJd wlf1 G.L 1. Copper : Rs 38,000/- ~-E)
fastenings (K ~ralabuilt) 2. Aluminium sheathing : Rs "' 12,000/- () ."' 3. FRP sheathing : Rs 29,000/- 0 "0-!~~ (2 layers) 1:> ""! .. 0 !:l () <:i';i-"' Reinforced Plastics (Single skin Fibreglass Calculated price "' "';:;: structure) More than () ...... Rs 12-14 Lakhs each on 5 hulls basis. 20 0 3 "' 1:> (a) 'E' Glass/Epoxy resin years. ....;::: Rs 8.50 Lakhs " " ~ (b) 'A' Glass/Polyester resin Q ;:;:o- p ~;:: Calculated price More than 20. ~.:li"' .... 4 Ferro-cement . ....;:;: w Rs 2.00 Lakhs years .:: -...1 ;;: w Q9 TABLE COMPARATIVE COST ESTIMATION FOR A STANDARD 1 OAL COMBINATION b5 JV 100 (30.3 m.) i:::
FISHING VESSEL BUILT OUT OF DIFFErENT MATERIALS. f'>)o ~ ;::! ~ .... ,.._ • 11 -~ ._.'.,) .... "' percen~Approximate price compared ;::.~ Special features (\) -;::: content ltage of in percentage. >l Remarks (') ;::: S, No. M:aterials for a 100' steel wei~:I~H_:_u~l._l ~_:::5:.____::-:H:-"u7:11:-s---:2:":5~H~t,.-;;-llls 0 11:: Merits Demerits ;:s ~ "' - vessel. ght. . .. ·· ~---- ·· - "" .. ~~~~~·-.-~~~~~~~,~~--~ -:::: ...... ~I=:: Ideal for high-seas Periodical maintena g :::::. ,.., ... 106.20 Standard size fishing conditions. nee is essential aga V> ,,., 1 Steel 100 100 100 100 for off-shore 0 ;:: Tons Cheaper investment inst marine corrosi .....,_,o ;:s fishing & quicker construe- on and fouling. tion. ;io-... (J c... (\) ...... '"" this Treatment with pre- Requires heavier ;:s (\)., .... Costlier at ...... ,(\) Wood 111.51 105 106 106 servative for a Ion- construction and 2 " 106 ~·~ size range. ;::. ger life is possible. constant hull main~ ;·. <5 tenance. <.Q 0 0 0""-"" Lowest materi- Lighter boat or Suf~ersunder bime- (J>a "'.... ~1weight but greater pay load; ~alhccontacts; requ- (\) 3 Aluminium 47.65 " 45 135 135 135 (\) p 1nitial high cost Lesser Horse Power 1res special painting ;:: -- or greater speed. schedule for the ~~ hull against fouling .... """' ~
WOODEN CRAFTS has successfully investigated the posibility of using treated timbers for the deck The chemical, physical and mechanical beams, deck planks, railings, bulk-heads properties of some of the be.:'t Indian and hatch covers in a wooden trawler woods with their easy workability have in lieu of the costlier untreated timbers won them a time honoured place in the which are now in use. It is still felt construction of fishing beats. This mate that the knowledge gained in timber te rial appears to be economical in boats of chnology has not been used to its fulle lengths between 30-60 feet (9 m-18 m) st extent in the wooden boat building but not above and below. However, the field. greatest handicap with wood is that its strength is nor uniform throughout and STEEL VES3ELS being an organic material, is very much susceptible for rapid deterioration under The versatility of steel as a constru the influence of various biological agen ction material for fishing boats is well cies and under adverse weather conditions known. As regards ordinary iron and which naturally limits their normal service steel for boat construction they are high life to about 10 to 12 years. The under ly susceptible to corrosion damages in water depradation of timber structures both costal atmosphere and sea-water in sea-water is so much that no wood and yet they have by far the greatest en hull can ever remain in sea-water .use because of the factors of cost and for long with 0ut adequate and costlier their important physical properties out protection. Wood, has also become scarce weigh all others. The ship building in since suitable boat-building timbers are dustry requires special type of steel for not now easily available either in the use. Carbon steel (mild steel) IS the required sizes or in adequate quantity. basic material for ships, hulls, buoys By 1975, it is felt, that in India there and most other large items of eqmp will be a gap of more than 100 percent ment in a marine environment. The con between the demand and the actual su ventional mild steel has an yield streng pply of timbers for industrial us~s. A th of 15 tonnes per square inch but durable and efficient method of hull with small alloying additions it can be protection ha'S also become quite costly increased to 20 to 22 t.p.s.i. some of the arid tim~ consuming. Time has thus come specially alloyed steels will have a co for the improved utilization of secondary rrosion resistance 4 to 6 times more species of timbers after careful seasoning that of ordinary mild structural steeL and wood preservation as substitutes for It is felt that so long as the displace the scarce conventional timbers like Teak, ment ships will continue to play the Aini and the like. Cheaper timbers like dominant role in sea trade, steel wiU Mango and Haldu after prior seasoning remain the most commonly used ship and treatment can be brought to exten hull material but may be high strength sive use in boat building with conside steels replace the present mild steel rable saving in cost and prolonged servi material in the coming years. How ce life as is shown in the following ta ever, the sea-water corrosion of bular statement. steel can only be controlled by external protective measures (painting) than by The Central Institute of fisheries the compositon of steel. Steel is ideally Technology, as _an experimental measure, suited for reasons of economy and quick
VoL X No 1 1973 39 13alasuGramanyan: Utilization of treated mood, steel, fiGreglass, ferrocement and aluminium in tfle construction of modern fisfling &oats and tlteir Comparative cost analysis. fabrication if the size ranges of boats production is envisaged with the use of are about 60 feet overall lengths and a single mould. FRP once popular for above. To-day ship building steel is life boats, rafts and pleasure crafts, has still in restricted supply and is being to-day taken a firm place for smaller carefully allotted at a quoted price of and medium sized trawlers also exclusi Rs.l600/- per ton. In spite of an en vely on the merits of its versatile chara couraging strength/weight/ cost ratio of cteristics. Considerable progress has since the material, steel trawlers require care been made and a notable event was the ful periodical maintenance particulary of publication by Lloyd's Register of shipp the hull below water-line and the wind ing of provisional rules for the applica water zone. Under adverse tropical cli tion of reinforced plastics to the con matic and hydrographical conditions, the struction of fishing craft from 20 ft. to life of steel trawlers in India can be 100 ft. (6 to 30.3 m.) long. To-day placed near about 15 to 20 years. The no other material is taken advantage of hull plates gradually thin out due to as much as FRP for larger sizes of corrosion. By constant. chipping and trawlers and sophisticated vessels inclu sera ping off the rust, eventually there ding hover-crafts and \'.rockets. FRP will be no steel left on the hull. When boats have already become popular in sea-water is of particulary ~irulent corro U.S.A., Canada and U.K. and other sive environment for most metals specia developing countries. Japan is planning lly steel, and also has a deteriorating to modernize about 350,000 small fish force and organic materials like wood, ing vessels with FRP as construction naturally the choice has to fall on a costs of wooden boat have gone very newer material which would be absolu very much up. A 54' (16. 3m.) FRP tely free from these problems. boat "SARDINELLA" imported from Norway is already in India (Cochin) FIBREGLASS REINFORCED PLASTICS (FRP) under the U.N.D.P. project. A private company has recently started manufactu FRP is a proven hull material pro ring FRP boats within India. viding satisfactory service in commercial, naval and pleasure crafts all over the As regards economics, FRP boats world. Of all the structural materials require greater initial investment and mi available at present Fibreglass Reinforced nimum expenditure on maintenance there Plastics is probably the most suitable after. The most essential raw materials group especially for boat building. Rein like fi breglass and thormosetting resins forced plastics with the use of ideal are very highly priced in India when materials like fibreglass and therm:)setting compared to world markets. The fibre resins offer a construction medium which glass material for the reinforcemem that is light, durable and astonishingly tough is now available in India is of alkali yielding to fabrication to any desired 'A' glass composition containing 10 to size and shape. The material is free 15% of alkali calculated as Na 2 0 much from corrosion both in air and water inferior to the 'E' glass. The lower and undergoes no deterioration at all at alkali 'E' glass composition which con the hands of biological agencies specially tains less than 1% alkali will give 10% the marine organisms. This new mate greater strength and better results under rial and the method of construction is adverse conditions than the 'A' glass. ideally suited for fishing boats where The resins most widely used with glass
40 FISHERY TECHNOLOGY 13alasut5ramanyan; Utilization of treated wood, steel, filheglass, ferrocement and aluminium in tfte constructions of modern fisliing f5oats and tfteir comparatiue cost analysis. fibre reinforcements belong to the Poly In a developing country like India with ester thermosetting group and where so many problems with wooden and superior physical and chemical proper steel fishing boats, FRP has apparently ties are required, epoxy resins are often a bright future. preferred. The cost of parent mould be cause of the excellent perfection that is FERRO CEMENT required, is sometimes 2 to 3 times cost To-day 'ferrocement' fishing boats lier than the off-spring hull. The con have become popular aU over the world cept of FRP shipyard is quite elaborate and this new construction material has and complicated besides being expensive been accepted and approved by Uoyds too. The technical know-how on FRP Register of shipping, Bureau of Veritas, fabrication of fishing boats is very much the United Kingdom White Fish Autho restricted in India at the moment. FRP rity and the Food and Agriculture Orga boat building is not merely assembling nisation of the United Nations. of preformed components as is in the case of wood and steel boat construction Not only Uoyds approved ferro-ce but a new structural material with the ment, but in January 1967, they have careful combination of fibreglass and produced their own standard rules for resin has to be made on the spot at an ferro-cement crafts thus giving the the time of fabrication. FRP is a uni new material international recognition. que material and full use must be made F.A.O. of the U.N. has studied in grea of its inherent properties in order to ter details with prototype constructions, obtain the best possible performance. the design and economic aspects of ferro-cement fishinig crafts. Investors A 32' (9.7 m.) class of vessel m from Germany and Japan are reported FRP made in India is now offered at to have shown considerable interest m Rs.76,000 for huH alone and in a ready the Ceylon Project to build a large for fishing condition at Rs.l ,25,000. number of ferrocement fishing boats. FRP boats require special design chara' Fishing vessels with hulls of ferrocement ctors and construction details as other' are gaining favour in the waters of NOr wise if built on the existing lines of thern Australia and a number of repeat wooden or steel vessds they tend to orders have been placed with the build float excessively and may not pr.Jve to ers. "Pak Tak" of Hong Kong (54.5' b~ a stable platform for fishing. This or 16.6 m.) and "Caranx" of the West· undue lightness should be taken to ad Indies (50 1 or 15.15 m.) are some of vantage in as many ways as possible the outstanding ferrocement boats work such as increased speed, increased fish ing most satisfactorily to-day in their hold capacity, greater endurance or less respective waters. er horse-power. A reasonable· reduction in the raw material cost and mass pro Realising the bright future for this duction of the standard designs of boats new material and the world-wide interest, in suitable size ranges will alone make F.A.O. of the United Nations had quite FRP boats an acceptable proposition recently organised a senior on the design under the present economic conditions and construction of ferro-cement fishing in India. No doubt FRP boats will vessels of Wellington in New zealand last longer than wood and steel counterparts during october 1972, when many newer with minimum care on their maintenances findings have come to light.
VoL X No 1 1973 41 'Balasu6r~manyan: Utilization of treated wood, steel, fioreglass, ferrocement and aluminium in tlie construction of medium fisliing 6oats and tlieir comparative analysis.
From an economical point of view, United Arab Republic where wood is scarce. experiences elsewere show that a size range Ferro-cement :boats are quite simple to of 401 to 601 (12.12 m. to 18.2 m.) ferro build and maintain and repairs are easy cement hulls are likely to give satis to make. They are not prey to marine factory service if constructed on standard borers which makes them ideal for use sound lines using the approved materials in tropical climates. Hulls can be per of steel, cement and sand besides clever fectly finished so that they sre virtually workmanship. It must be borne in mind indistinguishable from other materials", that ferro-cement boat construction und (F·A.O.). Well finished concrete hulls er reference differs very much from the do not absorb water and therefore there conventional Reinforced Cement Concrete is no risk or contamination in fishing (RCC) with which the Civil Engineers boats. Ferrocement structure is a very are familiar. good insulator having a thermal condu ctivity and consequently there is little Ferro-cement is a very thin ~~~ to 1" or no risk of condensation in concrete or 18 to 25 m m. thickness), highly hulls. It is interesting to note that "Ferro_ reinforced slab of concrete with four cement" structures become stronger and layers of galvanized iron chicken wire stronger with increasing age more espe mesh (20 SWF of ~ 0 hexogonal mesh) cially under constant contact with water. firmly fixed on either side of a pre Unlike FRP, ferrocement is immensely formed steel framework consisting of hard and shows great resistance to abra both vertical and horizontal rods of ~ » sion. Ferrocement boats if sound other (6.2 m m.) thickness placed 3" x 2" wise- will have the longest life in water (75 mm x 50 mm) apart. The mortar IS since reports prove to show that experi a mixture of high quality cement and mental boats built nearly 100 years ago sand which after careful mixing with are still structurally sound? water has to be forced through the den se layers of mesh leaving no voids any Based on theoretical calculations and where. The finished structure after cu with the limited experience we have ring should be absolutely water proof. with this new material, ferrocement boats The steel content will work out to app are likely to cost very much less than roximately 35 pounds per . cubic foot the conventional wooden hull. The con (562 kg. per cu.m.) while the mortar den struction procedures are simple requiring sity is 150 pounds per cubic foot (2:2 simple tools and ordinary unskilled ma tons per Cu,m.). A 50'(15.I5 m.) boat nual labour. If unrestricted supply of will have a huH thickness of not more steel rods and good quality cement are than 3" to 1" (19 to 25 mm.) with a assured this new material will catch up 4 . 1 density of approximate y 185 (2.97 tons a good market in the near future due to per Cu.m.) pounds! per cubic foot (Sp. its low cost, high strength and durabi_ gr.of 2.4 to 2 6). The outside hull will lity. receive suitable paint coatings before launching as a measure of protection ALUMINIUM FOR FISHING VESSELS against water seepage as well as marine foulants. The advancement in metallurgical science to-gether with the advancements ''Ferro-cement is competetive with in welding techniques have made possi other materials especiaUy in countries like ble the free use of aluminium magne-
42 FISHERY TECHNOLOGY 'Balasu6ramanyan: Utilization of treated wood, steel, fi6reglass, ferrocement and aluminium in tfte constructions of modern fisfiing f5oats and tfieir comparatipe cost analysis.
sium alloy to fishing vessel construction. son or other. The material is ideal for These special quality alloys are very lighter and faster coastal boats besides light (Sp. gr- 2.7 as against 7.9 for mild for drifters, gill netters and the like m steel) and have a high strength to weig spite of high investment involved. ht ratio. The marine quality alloys con taining 2 to 5% of magnessium are ex The table below will give a fairly tremely durable and they resist sea-wa good idea about the lightness of marine ter corrosion without water absorption, quality aluminium alloys where in the rotting, rusting and warping. The use weights of aluminium structures as a of this material will result in a light percent of an equivalent steel structure boat with high strength per weight, low are presented. centre of gravity for proper stability, Hull : 45 to 50% greater speed per horse power and a Super structure & Deckhouse : 35 to 40% minium cost of maintenance. Due to a Hatchcovers : 35 to 50% good elastic modulus, aluminium constru Lifeboats, Davits : 35% cticn has greater impact resistance than Ladders, Crattings & F]oors : 45% steel. Aluminium is non-sparking and It is seen that the individual chara non-magnetic. It is non-porous and cteristics of all the boat building mate non-peeling and provides a most desira rials mentioned above only show that ble hygienic condition for fish handling. the new materials like fibreglass reinfor Aluminium has high reflectivity and as ced plastics, ferro-cement and aluminium such insulation and refrigeration require if put to proper use can only relieve ments are simpler than steel and it has the present strain on the conventional thermal conductivity. materials like steel and wood. May be, we have to-doy a wider choice of con Aluminium is mostly not compatible structional materials for fishing boats. with other Conventional/metals more so in The newer materials cannot replace the sea-water due to electrolysis. Correct traditional ones all of a sudden but every welding procedures and techniques in one of th~m have their own place and dealing with aluTiinium are of great im significant role to play, either in their p )rtance. Its Io.v melting point ihas an individual capacity or in combination adverse effe.::t on the material and so with others. We must now look to ma also heat on its strength prop~rties. terials of the future if the progress is Sm::tller crafts are already operating in to continue steadily. The boat-building the Inland waters of India. The recent industry like any other, is constantly ly introduced 57' (17.10 m) steel traw looking for new materials to make better, lers have their superstructures built out mJre compete-tive and more durable fish of marine quality aluminium and this ing bJats. This demand and necessity have will improve the stability of the vessel created a new technology - "The Science by lessening the top heaviness. India of Materials," can make the best use of this indige_ nous material for fishing boat construc ACKNOWLEDGEMENT tion not only for the hull but also for The author is thankful to Dr. V. K. various other ship-board applications in Pillai, Director, C.I.F.T. and Shri G. K. cluding fish-holds, containers etc· to a Kuriyan Head of Division (Craft & Gear) great advantage wherever other conven- , for helpful suggestions inpreparing this tional materials have failed for one rea- paper.
VoL X No 1 1973 43