
This
is one of the most interesting processes for amateur construction. The
final quality of the boat is excellent, there is no need to build expensive
plugs or moulds, and the building technique is quite simple. When the
work is completed, the ply-glass boat is absolutely watertight and the
final quality is long lasting and requires very little maintenance. A
ply-glass hull has all the advantages of fibreglass reinforced plastic
and still keeps the warmth and tradition of a wooden interior. Ply-glass
boats use plywood as a primary material and hull and superstructure are
sheeted with it. After the plywood sheeting is completed a thick glass
fibre lamination is applied over the whole hull and superstructure as
well. Once deck lamination overlaps hull lamination, the boat is seamlessly
encapsulated, giving no possibility to deck-hull joint leakage. Plywood
practically only bends in one direction, and doesn't accept compound curves
For that matter ply-glass hulls are of chine construction, generating
flat segments in transverse sections. When they are more than one chine
each side, the hulls are called of the multichine type. If properly designed
multichine hulls are as attractive as round bilge hulls and the difference
in performance is practically negligible.The method of construction starts
with the confection at the workbench of transverse frames and bulkheads
and next this transverse structure is put in place over a strongback with
the aid of the longitudinal structure of chines, sheer clamps, keel and
stem. Following the whole structure is faired and plywood is glued over
it. Next, glass-fibre, preferably saturated with epoxy, is applied over
the hull which must be built upside down. The lamination isn't merely
a protection for the plywood. In the ply-glass method of construction
the lamination is strong enough to work as a structural component and
once the plywood also has a structural role in the whole process, the
result is an immensely strong and rigid monoblock of relatively light
construction.

To help the overall strength of the structure, all transverse and longitudinal
furniture are glued in place collaborating this way for the stiffness
of the boat. Internally, two coats of epoxy resin must be applied all
over the boat, except in places where a varnish finishing is wanted. In
these places the epoxy should be substituted by the chosen type of varnish.
The construction by the ply-glass method is simple and requires no skilled
knowledge but, once the glass-fibre lamination isn't performed inside
a mould, the external surface must be sanded until the surface is smooth
enough to be considered a high level of finishing standard. This work
is laborious and requires patience mainly to accept the discomfort of
glass sanding. But after this task is accomplished, and after all it isn't
so difficult to do it, the final result is by far superior than the standard
gel coat inishing commonly used in production boats. The ply glass boat
is painted instead, using preferably polyurethane, a much better product
than the best gel coat available, so ply glass boats tend to have more
longevity and no tendency to show osmotic infiltration. A good example
of the durability of ply-glass boats is the Multichine 23, Caso Sério.
This boat was built in 1980 and despite staying in the water for all this
time, she is in perfect condition by far surpassing the state of conservation
of most contemporary series produced glass boats. It's important to explain
some important points about ply-glass construction that are misunderstood
by the less acquainted with the system. The first point that needs to
be revised is the idea that wood must breath.This is a fallacy. What breaths
is the fungus responsible for dry-rot. When epoxy saturates the pores
of wood or plywood, they become impermeable to moisture and oxygen, and
rot doesn't occur. For that reason the ply-glass boat as well as a cold
moulded hull, should be thoroughly impregnated internally with epoxy.
The other point to be considered is the durability of the bonding between
glass-fibre and plywood. If plywood is contaminated with grease, paint
or humidity bonding isn't good. So it's important that the plywood surface
is free from these contaminants. Besides there are two factors that are
essential for a good result. The usage of epoxy resin for wetting the
glass-fibre, considering the superior bonding properties

of
the epoxies over poliester resins, and last but not least, the glass reinforcement
shall be responsible for an important part in the structure of the boat.
Being less important structurally in the process, plywood works primarily
as a moulding base, giving no possibility to future delaminations. This
is of so great influence in the final result, that even whenpoliester
resin is used when glass fibre is thick enough to assure sufficient strength
to the structure, there is no possibility of delamination. Taking into
account those recommendations ply-glass boats are easy to be built, strong
and long lasting, and the process constitutes one of the most successful
methods of construction available.