Wooden test panels of different species of wood sheathed with fibre-glass reinforced plastic were subjected to immersion tests along with corresponding controls in Cochin Port area and the effect of the protective coating studied

Balasubramanyan, R.

Aquatic Commons

PE I ENTS T 
G 
B E-GLASS S EAT I G AS 
o .. ao NG ST E 
RGA ~S S 
R BALASUBRAMANYAN 
Central Institute of Fisheries Technology, Croft & Gear Wing, Cochin-5 
Wooden test panels of different species of wood sheathed with 
fibre-glass reinforced plastic were subjected to immersion tests 
along with corresponding controls in Cochin Port area and the effect 
of the protective coating studied. 
INTRODUCTION 
Wooden bulls of fishing boats that are 
constantly in contact with sea-water (huH 
below water-line) are subject to rapid de-
struction by the attack of many marine 
wood-boring organisms on them. · The 
indigenous timbers that are now in use in 
~sbing boat construction are not able to 
resist the borer attack for a cons.iderable 
length of time unless they are adequately 
protecced (Baiasubramanyan 1963). Shea-
(Continued from page 59) 
Tarr, H. L.A., 1961, in "Fish as Food". 
Editor- G. Borgstorm. VoL I p. 639. 
Ne_w York, London. Academic Press. 
Tomiyama, T, 1962, Bull. Jap. Soc. Sci. 
Fish., 28, 86 
Tomiyama, T, Tsuda, A. and Yone Y., 
1960 a, Food Res., 25, 97-'-106 
--- and_--- 1 1960 b, Ibid., 
pp, 106-112. 
Velankar, N. K. and Kamasastri, P. V., 
1957, Indian J. Fish. 1 5, 150 
60 
thing the wooden bull below water-line 
either with copper or aluminium alloy 
plates is the weB known. conventional pro.; 
tective measure that is now being adopted. 
British Patent No. 82430l describes a 
protective sheathing process for' wooden 
vessels wherein treated nylon cloth and 
resorcinal resin form a tough impervious 
coating on the hull which becomes comp-
letely resistant to marine borers. The use 
of fibreglass in boat-building industry has 
Visweswariah, K Moorjani, M. N., Bhatia, 
D. S. and Subramanian, V., 1959, J. 
Fish. Res. Bd. Can., 16, 1. 
WrenshaU, C. L., 1957, Antibiotics Annual, 
1956-57 p. 809. New York Medical 
Encyclopedia Inc. 
Yone, Y, 1962, Bull. Jap. Soc. Sci. Fish., 
28, 92. 
FISHERY TECHNOLOGY 
increased considerably over the last few 
years. Though fibreglass is extensively used 
as an insu]ant in fish-holds and cold rooms, 
practically no effort bas so far been made 
to evaluate the exact resistance of fibreglass 
reinforced plastic sheathing on wooden 
hulls as a measure of protection against 
the marine organisms. 
Investigations on the use of fibreglass 
sheathing as a substitute for the conven-
tional copper or aluminium alloy plates on 
the hulls of the modern mechanised fishing 
boats and the extent of protection that could 
be obtained by this new sheathing material 
against the marine wood boring and foul-
ing organisms in the tropical warm waters 
of India are presented in this paper. 
MATERIALS AND METHODS 
Well seasoned wooden t.::st blocks 
measuring 15cm X 6cm X 3. 75cru each were 
selected for the purpose of sheathing them 
with fibre-glass materiaL Aini ro Anjili 
( Artocarpus hirsuta), Mango (Mangifera 
indica) and Haldu (Adina cardifolia) were 
the different boat building timbers chosen 
along with marine grade plywood panels 
manufactured to Indian Standard $pecific-
ation using White Cedar (Dysoxy!um mafa-
baricum) for the face and 'Pali' (Palanquim 
ellipiicum) for the core. The sheathing 
material for the reinforcement was the in-
digenous fibre-glass chopped strand mat 
weighing approximately ltoz per sq ft. 
(450g./m2 ). The resin used was a polye-
ster variety with Methyl ethyl ketone per-
oxide as the catalyst and Cobalt naphthe~ 
nate as the accelerator. 
The bare wooden surfaces of the test 
boards were first thoroughly wetted with 
resin and a layer of fi breglass chopped 
strand mat of the above specification was 
laid and pressed with a paint brush with a 
further quantity of the resin. After parti-
al drying of the surface, a second layer of 
fibre glass mat was also fixed and the sur-
VoL VIII No. 1 1971 
face wetted uniformly using a resin soaked 
brush (Fig l). Each wooden test board 
was completely sheathed on all sides inch.i-
ding the narrow ends. Post curing for a 
period of 4 weeks under room temperature 
was allowed before the panels were proq 
perly marked foreasy identification. One 
set of wooden test blocks without shea-
thing was used as control for comparison. 
RESULTS 
The test boards prepared were fixed 
in specially fabricated racks and immersed 
at suitable depth at different locations in 
the Port of Cochin (Kera]a, India) where 
the marine organisms were predominant 
and at a time when they showed maximum 
amount of settlement. The exposed panels 
were lifted for inspection once in thirty 
days for a period of one year during 1962-
63 and the general conditions of the test 
boards as well as the quantity and quality 
of the marine organisms that settled on 
them and more particularly the surface 
borer holes were carefully noted and recor~ 
ded. The fouling organisms were scraped 
off the panels at the end of every inspection 
so as to accelerate further borer attack 
without any possible impediment due to 
fouling. 
Hydrographical data mainly compri-
sing of water temperature, salinity, pH and 
dissolved oxygen at the test site for the 
entire period of observation were recorded 
Fig 1. 'Wooden test panels being sheathed with 
fibreglass reinforced plastics (FRP) 
6! 
TABLE I MONTHLY AVERAGES OF THE HYDROGRAPHICAL FACTORS 
AT THE TEST SITE DURING 1962-1963. 
Hydrographical Sept Oct Nov Dec Jan 
details 1962 1962 1962 1962 1963 
Water tempera-
ture.0°C 29 29.5 31.0 30.2 28.2 
Salinity %o 2.65 3.58 12.1 28.7 29.0 
pH 7.5 7.5 7.6 7.9 
Dissolved 
oxygen ml/] 6.0 6.1 8.0 5.8 
(Table 1). and all the marine organisms 
encountered were listed. At the end of an 
year's continuous exposure, the panels 
were withdrawn and the condition of each 
was critically exa 'Tiined with a view to 
assessing the damages caused by the 
marine organisms and the efficiency of the 
new protective sheathing material. 
The surface borer holes were carefully 
noted by actual counting and the external 
damages expressed as % of the total area 
exposed (Balasu bramanyan, Joe cit). By 
scraping the surface and peeling off the 
sheathing materiaJ, further examination 
was made to record their conditions. The 
marine plywood was carefully de-laminated 
to ascertain internal timber damage caused 
by the different wood borers. The obser-
vations on the control panels are presented 
in Table II. It is seen from the table that 
none of the controls survived beyond 11 
months of immersion. But all the sheathed 
panels were in tact with no external or 
internal damage even after one year of con-
tinuous immersion. The attack on control 
panels was mostly by Martesia striata, 
Nausitoralhedleyi, Teredo furcilfatus and 
Sphaeroma terabrans. 
At the final inspection at the end of 
360 days of continuous immersion to the 
free attack of the marine organisms, all the 
fibre glass sheathed wooden panels pro-
vided a normal settling surface to most of 
the common fouling organisms as the un-
sheathed controls did. 
62 
7.4 
4.5 
Feb March April May June July Aug 
1963 1963 1963 1963 1963 1963 1963 
28.7 31.1 31.4 31.4 29.1 28.6 28.4 
31.0 30.5 29.9 27.0 15.7 2.8 2.1 
7.6 7.4 7.5 7.5 7.6 7.5 7.5 
5.2 6.0 4.9 5.0 5,5 5.9 6.9 
TABLE 2 MARINE WOOD BORER ATTACK ON 
CONTROL PANELS OF DIFFERENT 
SPECIES OF TIMBERS 
(Value expressed as% of total area attacked) 
-
Month of Artocarpus Mangi- Adina Marine 
ohaervation hirsuta fer a cordi plywood 
indica folia 
~---
Sep '62 Nil Nil Nil Nil 
Oct. , !0 20 20 15 
Nov,. 25 35 30 25 
Dec , 35 45 40 30 
Jan '63 40 55 50 35 
Feb ., 45 60 55 45 
Mar , 50 75 65 55 
Apr 
" 
55 IOO 80 70 
(removed) 
May, 70 90 85 
Jun .. 85 100 100 
(re- (re-
moved) moved) 
Jul 100 
(removed) 
The chief marine wood borers of India 
are 2 species of Martesia, 28 species of 
ship-worms, a variety of Sphaeroma inclu-
ding 4 identified species and 9 species of 
Limnoria, of which all the. 2 species of 
Martesia, 11 species of ship-worms and 3 
species of Sphaeroma have been reported 
to be present in the Cochin waters (Nair 
1964). At the Central Institute of Fisheries 
Technol9gy test site where the present 
exposure studies were conducted, the 
author has reported that Nausitora hedleyi, 
Martesia striata and Sphaeroma terebrans 
were the most devastating wood borers 
FISHERY TECHNOLOGY 
that often show a maximum density of 
occurrence (Balasubramanyan 1963). Du-
ring the current observation, the presence 
of Teredo {urcillatus at the test site has 
also been recorded in addition to the above 
mentioned organisms. 
The unsheathed controh exhibited the 
first evidence of borer attack during the 
second inspection in the month of October 
as revealed by the presence of surface 
holes. The borer attack appears to have 
been initiated on the unprotected controls 
roughly between 40 and 45days of immer-
sion. At every inspection it wa~ observed 
that the attack of the marine wood borers 
on the unprotected controls were on the 
increase and before 6 months were com-
pleted, more than 50°fo damages were noted 
on them (Figs, 2 .& 3). The fibre glass 
sheathed wooden test panels were however 
free from any damage. The timber dama-
ges were caused mostly by Martesia striata 
(80%) and to a lesser extent by Nausitora 
Fig 2 & 3. Pattern of marine borer attack on 
unprotected wooden test blocks ( contrel) 
at the C. I. F. T Test Site, Cochin. 
VoL VIII No. 1 1971 
hedley; and Teredo furcil!atus (20%). As 
regards the hydrographical features at the 
test site, salinity of the water appears to 
have the greatest influence on the marine 
boring and fouling organisms. From 
November onwards tiH May the salinity of 
the water was steadily increasing and sim-
ultaneously the quality and quantity of the 
marine organisms were on the increase as 
observed previously by Bala.subramanyan 
(foe cit.) and Nair (1965). rt was inte-
resting to note that the acorn barnacles, 
Balanus amphitrite, which are known to 
plough into paint coatings with the sharp 
growing edges of their shells could not do 
so with the fibre-glass sheathing though 
they were settling on them in large 
numbers. 
DISCUSSION 
Ply-wood specially fabricated and re. 
commended for the construction of marine 
crafts in an untreated condition is liable to 
be severely damaged by marine wood 
borers under prolonged immersion as wit-
nessed during the present investigation. 
Both the species of timbers 'White cedar' 
(Dysoxylum mafabaricum) and 'Pali' (Pa-
lanquium elfipticum) like the other varieties 
do not possess adequate natural resistance 
against marine borers. 
The fibre glass reinforced plastic 
should undoubtedly be credited for its 
special characteristics as a sheathing mate-
rial as it withstood the continuous im-
mersion without being attacked by Marte~ia 
striata (Fig 4) which is considered to be 
notorious for its boring habits. This pho-
Jadid is capable of boring into st~nes, coral 
rocb, lead sheathing, brick works and 
concrete structures, (Annandale, 1923, 
McGlashan, 1924, Springer et, a! 1960). 
An instance of Martesia striata repeatedly 
attacking plastic sheets (PERSPEX -
Methyl methacrylate) of 1/8" thickness in 
the Port of Cochin has been reported by 
the present author (1965). 
63 
Fig 4. Wooden panels at the end of an year's 
marine exposure test. FRP sheathed (No.4) 
panel is free from both external and internal 
damages due to marine wood borers. 
Apart from being tough, rigid, resis-
tant to abrasion and impervious to the 
effect of salt water even under continuous 
immersion, fibre-glass sheathing in com-
bination with polyester resin has shown 
promise of protecting timber structures 
against marine borer attack for an extended 
period. It has been reported not to rot, 
nor leak or open up at seams, corrode, or 
absorb water and become heavier, (Fabre 
1954). T.be wood below the sheathing has 
been safe and sound. The present obser-
vations suggest that the non-metallic shea-
thing materiab should be finished with a 
top-coat of suitable anti-fouling paint so as 
to reliably ward off the marine borers and 
foulers. Nylon fabric has also been suc-
cessfully employed as a sheathing material 
elsewhere. Tests conducted at the Tropical 
Testing Establishment have revealed th:~t 
the African Mahogany (Khaya ivorensis), 
a timber very susceptible to ship worm 
attack has been successfully protected by 
nylon fabric sheathing for 49 weeks at Port 
Harcourt, Nigeria, while the unprotected 
controls were completely destroyed in less 
than half this period (Anon 1958). The 
Baltic Red-wood (Pinus sylvestris) she-
athed with nylon fabric has been free from 
the marine wood borers- like Teredo sp. 
and Limnoria sp, in Shoreham Harbour 
(Oliver 1961). 
64 
Whatever material is tried and recom= 
mended as the non-metaBic sheathing for 
hull protection, it must very reliably resist 
all the marine wood boring organisms in 
Indian waters more particularly the erratic 
attack of Martesia striata. The problem 
of successfully protecting the wooden hulls 
of fishing boats with non-metaUic shea-
thing materials like fibre-glass and nylon 
fabric still offers a virgin field for further 
research in India. 
SUMMARY 
In the Port of Cochin in India where 
most of the timber destroying marine wood 
borers (Teredinids 1 Pholadids and Crusta-
aceans except Limnoria) are present in 
large numbers, wooden test panels and 
marine ply wood test boards protected with 
a sheathing of fibre-glass re-inforced 
plastic have been free from all borer 
attacks for a period of 52 weeks while un= 
protected controls were all attacked heavily 
within 25 weeks during a marine exposure 
test. 
ACKNOWLEDGEMENT 
The author is grateful to M/s AFCO 
Ltd., Bombay, M/s Fibreglass Pilkington 
Ltd., Bombay and M/s Hylam Ltd., 
Hyderabad for kindly making available the 
necessary samples of fibre-glass and resin 
for the investigations. 
REFERENCES 
Anon., 1958, "Nylon sheathing- protection 
of timber against shipworm'', Ministry 
of supply, Tropical testing- establi-
shment, Port Harcourt, Nigeria. 
Annandale, N., 1923, J. Asiat. Soc. Bengal 
18, 55 
Balasubramanyan, R. 1963, J. Mar. Bioi. 
Ass India, 5 (2), 294-310. 
----, 1964, "Protection of wooden 
hulls of fishing boats against marine 
borers". Paper presented at the 
Symposium on 'Marine Paints'. Def-
FISHERY TECHNOLOGY 


Experiments with fibre-glass sheathing as a protection against marine wood-boring organisms

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Experiments with fibre-glass sheathing as a protection against marine wood-boring organisms

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