The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 15 – Coating and Finishing 155
Second and Subsequent Epoxy Coatings
Use a foam roller to apply the second coat of WEST
SYSTEM epoxy. <strong>The</strong> important goal now is a smooth
coated surface, and for this you need long, vigorous
strokes. Roll the epoxy in several directions to maintain
as even a film as possible. If you inadvertently apply too
much epoxy to an area, it may run. Cold epoxy is difficult
to apply in a uniform film, so use only warm epoxy
on second coatings. Use a brush to remove any air
bubbles or stipple, following the guidelines mentioned
earlier in this chapter.
Apply at least one penetration coat and one secondary
coat to every surface inside your boat. It is possible to
remove one or more coats of epoxy during sanding, so
areas which require a lot of abrading will require a
minimum of three coats of epoxy. You can apply more
coatings and they will provide greater resistance to the
elements, but generally you reach a point of diminishing
returns in both practical and economic effectiveness
with more than three net coats of WEST SYSTEM epoxy.
However, we do recommend applying up to six coats of
epoxy on surfaces that will be below the waterline on
boats that stay in the water for months or more at a time.
<strong>The</strong> smoother the surface coating, the less sanding you
will need for a really smooth finish for final painting. In
many cases, you can leave the second or third coating
as is in interiors and other areas which have no need of
a decorative coat of paint or varnish. Make provisions
for final finishing your exterior early, however.
Samples coated at our shop show a coverage rate of
40 square feet per pound (8.2m2 /kg) of applied mixed
epoxy. Since 2 oz (60g) of epoxy can be wasted in a roller
cover and some film may remain in a roller tray or
mixture pot, actual coverage may be reduced by up
to 25%. A fair average application rate for estimating
material costs and weights for initial and secondary
coatings WEST SYSTEM epoxy is 35 square feet per
pound (7.2m2 /kg) of mixed epoxy.
WEST SYSTEM Pigments and Other Additives
Pigments and other specialized additives may be added
to the epoxy used in secondary and final coatings. Since
they may affect penetration, we advise against using
these materials in initial coatings. See Chapter 4 for
detailed information on these products.
Figure 15-3 Building up epoxy coating on the deck of the
proa Slingshot. Note that the topsides and bottom have been
coated with gray pigmented epoxy.
Figure 15-4 Bottom of the proa Slingshot has been coated
with gray 420 Aluminum Powder pigmented epoxy and
sanded in preparation for painting.
WEST SYSTEM white and gray pigments cannot, of course,
be used on naturally finished hulls. However, if you plan
to paint your boat, they can be quite helpful. During
coating applications, pigments aid in maintaining visual
control of film thickness, and during sanding they can
prevent the removal of too much substrate. Pigmented
epoxy can also serve as a colored painting base, so
fewer coats of final finish are needed to cover a hull.
Both pigments and WEST SYSTEM 420 Aluminum
Powder provide protection from sunlight. Epoxy breaks
down under prolonged exposure to ultraviolet light; if
you do not plan to coat your hull with a finish system
immediately, add either pigment or powder to your last