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< prev - next > Fisheries KnO 100390_Plywood boats in South India (Printable PDF)
Plywood boats
Practical Action
who had the interests of the fishermen in mind?
BBC Muttom, CAT,
ITDG, and Gifford
discussed these
issues with the
South Indian
Federation of
Fishermen Societies
(SIFFS), a non-
federation of
Following this the
patent rights were
transferred to SIFFS
and they granted
BBC Muttom the
status of associate
member, thus
beginning a new
form of more
institutional linkages
and initiatives to
diffuse the
technology. SIFFS
opened a small
boatyard in the
fishing village of
Alljellgo in January
1983, and started
producing the first
kottarkat models
before specialising
in the plywood
New inventions are
never perfect at
first, and may
initially offer only
very small
advantages over
previously existing
techniques. The rate
and extent of
diffusion will
therefore depend on
the experience of
the initial adopters,
the availability of
innovations, and the
improvements made
to upgrade the
existing technologies.
Box 2 Plywood and boat building
Marine plywood is an extremely versatile and economic boat-building material,
with the following characteristics:
High strength-to-weight ratio because of the alternating direction of
the grain in the veneer and compression forces, and means that
thinner sections can be used, compared to traditional timber boat-
building techniques.
Great versatility, because it is not constrained by the shape and
characteristics of solid trunks or wooden planks.
Fewer seams or joints are required compared to planks, because of the
large size of the basic sheets
Plywood makes much better use of scarce resources than timber
Stitch-and-glue is widely used and simple
It was made famous by the Daily Mirror through the design for a kit boat for
hobbyist sailors – “The Mirror Dingy”. In Kerala a number of industries
manufacture marine plywood. The stitch-and-glue plywood technology requires
the use of the same carpentry skills needed for traditional boat-building,
coupled with skills in the use of fibreglass and resin system. The building
system is very versatile and can be readily adapted to a variety of craft designs.
It is, a technology which indigenous industries can use and which uses locally
available skills.
To use stitch-and-glue technique plywood panels are cut to predetermined
shapes, which are designed so that when their edges are joined, they pull
together to form the hull shape. The boat designer needs to consider the most
economical use of the plywood sheets. Cut-to-shape plywood panels are literally
stitched together with wire ties (the panels having had their edges pre-drilled
with holes to receive the wire ties). Ideally the wire used should be 18SWG
(Steel Wire Gauge) galvanized soft iron wire. If galvanised wire is not available,
however, then plain wire may be used, as it is finally covered with epoxy resin
and fibreglass tape.
A good ‘Exterior Grade’ or ‘Marine Plywood’ must be used, so it does not
delaminate when immersed for a long time in seawater. Ideally, plywood
conforming to BS 1088 should be used, particular care should be taken to
protect the exposed edges with epoxy resin and fibreglass tape.
The panels are held together by a very strong composite of epoxy resin and
fibreglass rovings (bundles of fibres). This not only provides an extremely tough
and resilient bond between the panels, but also results in a fully waterproof
seam. An additional benefit is that the plywood edges are completely sealed
too, protecting them from the elements. ‘Woven Rovings’ (a cloth of woven
glass rovings a roving being a bundle of very fine fibres) are the correct
reinforcement and carrier for the epoxy resin. In India this is not available in
tape form, the way it is in the North, so strips 1 to 2 inches (25 to 50 mm)
wide are cut from large rolls of woven cloth. It is important to note that in
fibreglass products dissolvable binders are used to hold the fibre together
temporarily (for handing and cutting). This is particularly so with chopped
Strand Mat (CSM). There are different types of binders too. Some are designed
to dissolve in polyester resin, others in epoxy, so it is important to choose
CIBA-GEIGY Araldite AY103 + Hardener HY951 should be used for fibreglass
work, and Araldite AW106 + HV953U for woodwork, or the equivalent epoxy
After the main hull has been constructed in plywood, the frame, bulkheads,
and thwarts, etc., are added using a durable boat-building timber (such as