The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

38 Fundamentals of Wood/Epoxy Composite Boatbuilding
Small dinghies, for example, are lightest when built
with the mold method, so it is often used for day sailing
dinghies and small offshore boats. Although the mold
method can theoretically be used on any size hull—
the largest mold we ever built was for a 30' (9.1m)
boat—quicker, more efficient, and more cost-effective
methods are available for large boats.
<strong>The</strong> Strip Plank/Veneer Method
for Larger Boats
Because of the expense of the mold and the labor
needed to install interior members, it’s often hard to
justify the use of the mold method on larger one-off
hulls. To get around these extra costs, some builders
use the mold as part of the hull. Many molds are strip
planked anyway; with the strip plank/veneer method,
the planking becomes part of the structure itself and
does not remain part of the mold. Strip planking is
efficient and economical for many boats, but it is
especially suitable for bigger custom boats.
While hulls have been planked with edge-glued strips of
wood for many years, larger strip planked boats rely on
intricate interior framework for athwartship strength and
stiffness. <strong>The</strong> alternative to interior support, sheathing
the planking with fiberglass cloth as is done with stripper
canoes, does not provide enough strength for very large
hulls. We discovered, however, that we can build an
exceptionally rigid and strong monocoque by using the
basic strip planked hull as a form over which to laminate
diagonal layers of veneer. <strong>The</strong> layers of exterior veneer
eliminate or reduce much of the interior framework
associated with larger wooden boats
With the strip plank method, it is advantageous to
install many major bulkheads in the boat during the
set-up and to form the hull right around them. This
saves time later because it is usually much easier to
install bulkheads before planking than to tediously fit
them in a finished hull. In a large, one-off project,
including internal structure in the set-up can significantly
reduce labor. Too many interior members may,
however, get in the way of sanding interior planking.
Strip planked hulls have thick, load-bearing wooden
skins. <strong>The</strong>y are reasonably light with high strength and
stiffness-to-weight ratios. As a bonus, the thickness of
a strip planked hull provides excellent insulation from
noise and temperature, and it may also reduce condensation
problems. Practical considerations generally limit
the use of the strip plank/veneer method to boats of
perhaps 30' (9m) or more, although some heavier
displacement, shorter, oceangoing cruisers have been
built with this technique.
Hull thickness is in fact a major consideration in
successful use of the strip plank method. <strong>The</strong> mold
must be stiff enough to support layers of laminated
veneer, so at least 1 ⁄2" (12mm) planking is usually used
on larger boats. For support with minimal interior
framing, we recommend that this be covered with no
less than three layers of 1 ⁄8" (3mm) veneer. <strong>The</strong> resulting
7 ⁄8" (22mm) hull will weigh a bit over 2 pounds per
square foot (.98kg/m2 ), and this may be too heavy for
smaller boats. While the edges of thicker planks can
be aligned with dowels or nails, thinner planking may be
stapled during edge gluing. No matter which is used,
the strip plank/veneer method is not particularly quick
when compared to other laminating techniques.
It should be noted that with a light, strong hull and
clean interior, this strip plank/veneer method of
construction has proven to be very successful in the
largest boats (Bruce King’s magnificent yachts are prime
examples). It is the preferred method for building larger
wood/epoxy composite boats to approval under Lloyd’s
or other certifying agencies.
Figure 5-4 <strong>The</strong> 124' (37.7m), Bruce King designed, sloop
Antonisa was built by Hodgdon Yachts, Inc. using the strip
plank/veneer method. Hulls as large as 213' (65m) have
been built with this method.