The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

296 Hull Construction Methods
2" wide nylon webbing
bonded with epoxy
and colloidal silica mixture
Figure 25-4 Joining plywood hull panels with nylon webbing.
nylon webbing system. If you use tape, however, apply
it to a clean surface and be sure to remove any adhesive
residue as soon as the webbing is firmly in place. Wash
any surfaces to which tape has been attached with
solvent and then sand them.
Nylon webbing, similar to seat belt material, maintains
better panel alignment than wire, especially around the
stem area, and usually eliminates the task of straightening
panel edges. To install it, round the inner edges
of the plywood to a 1 ⁄16" (1mm) radius and bevel a 45°
angle from the curved area to the outer surface. Join the
panels, interior surfaces facing, along the stem and keel
Bring plywood panels
together for tying
with wire
Drill 1 ⁄8"
holes for
copper
tie wires
Chamfer edge of panels
to aid in alignment
Plywood panels spread
to desired angle
Thoroughly clean all
tape residue and sand
inner keel area
Tape
Figure 25-5 Joining plywood hull panels with wire.
Radius & bevel
edge of plywood
Keep wires loose
enough to allow
plywood panels
to spread out
to keel angle
lines with carpet tape, clamp slightly, and check alignment.
Bond the webbing to the outside of the keel joint
with a thickened mixture of 406 Colloidal Silica and
epoxy, holding it in place with spring clamps until the
epoxy cures. Do not substitute fiberglass cloth tape for
the webbing since fiberglass cloth is too brittle when
wet with epoxy to be used in this application. Webbing
could be difficult to work with on asymmetrical hulls.
To use wires to hold the panels, lay out wiring holes
along the keel line and bow (also the stern if the hull is
a double-ender). <strong>The</strong>se holes should usually be about
1 3 1 ⁄8" (3mm) in diameter, ⁄8" (9mm) to ⁄2" (12mm) in from
the edges of the plywood, and about 4" (100mm) apart.
<strong>The</strong> holes on the two panels should be perfectly
aligned, so double check them before drilling. Next,
shape the inside facing edges. <strong>The</strong> easiest way to do this
is to stack the pieces on top of one another, clamp
them, and round them both in one operation. <strong>The</strong>n
place the panels on top of each with the interiors faceto-face.
Cut No. 12 ground wire or other lightweight
copper wire to about 5" (130mm) lengths, thread a
piece through each set of holes, bend it around, and
twist the ends loosely together as in Figure 25-5. Leave
enough slack so that the wire will not dig into the
wood when the panels are spread apart. We usually
wire panels together along the keel to the top of the
bow at the sheer line, but occasionally we leave the
bow open at this stage to help develop more fullness
along the keel line in that area. If you are building a
double-ender, also wire or tape the stern.
When the panels are wired or held together with
webbing, set them upright and begin opening them like
a book. To distribute the weight of the panels evenly
and better control the process, place sawhorses under
the keel about one quarter of the hull length in from
each end. Cut some sticks to length and insert them
between the sheer clamps to hold the panels apart (see
Figure 25-6) and then measure the keel angle between
the panels. As you spread the panels, clamp braces
from the sawhorses to the sheer clamps on either side
to make the unwieldy structure more manageable.
<strong>The</strong>re usually isn’t much stability at this point—the
panels are very wobbly.
We usually measure angles at three distinct parts of the
keel line and let the rest of the hull fall fair between