The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

222 Hull Construction Methods
set-up. Gaps between ribbands may be wider than the
ribbands themselves so that only 40 or 50% of the
mold surface is solid wood. Because staples can only
be inserted where there are ribbands, we mark the first
and second layers of veneer before fastening them. This
takes extra time, but since a ribband mold is quicker
to build than a planked one, the balance may lie in its
favor when it will be used for only one or two boats.
Somewhere between these extremes lies the mold that
is adequate for laminating most hulls. <strong>The</strong> quality of
a mold is most important as the first two layers are
laminated, when long staples are used to hold the
veneers snug against it. Staples may be inserted
anywhere in it, so a solid plug has a distinct advantage
during this stage. One less elaborate way to build a
strong, rigid planked mold is to laminate two layers
of 1 ⁄8" (3mm) veneer over an open, stringer mold.
Production Boatbuilding Molds
Production boatbuilding molds come in two varieties
commonly referred to as male and female molds. Male
molds have convex surfaces and female molds have
concave surfaces. Parts built on male molds are smooth
on the inside surface (for example, a cockpit liner) and
Added framework and legs
Top (deck) mold half
Plug
Top and bottom mold
halves are split at the
widest point of the plug
A temporary shelf
attached to the plug
gives a finished edge
to the molds
rough on the outside. Parts built in female molds are
smooth on the outside (for example, a cabin roof) and
rougher on the inside.
When producing hundreds of boat hulls, it is important
to reduce labor costs, so these boats are built in female
molds so that the outside of the part comes out of the
mold finished. <strong>The</strong> opposite is true of parts built on
a male mold. <strong>The</strong> inside is smooth and the outside
requires considerable labor to fair it and paint it.
Hence, a male mold is useful only for one-of-a-kind
boats.
Female molds are almost always built on a highly
polished plug because it is much easier to finish a
convex surface than a concave surface.
Setting Up the Mold
<strong>The</strong> first step in manufacturing the mold is to set up
the frames and forms onto which you will assemble the
longitudinal ribbands. <strong>The</strong> principles of construction
and set-up for mold frames are discussed in Chapter 18.
<strong>The</strong> materials used to construct the mold frames must
be structurally adequate, cheap, and have an edge thick
enough to receive a fastener so that you can attach
Bottom (hull)
mold half
Added framework
and legs
Figure 20-1 Building female molds from a single plug. <strong>The</strong> fine polished finish on the plug transfers to the inside of the mold
and to the outside of the finished part.