The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 23 – Strip Plank Laminated Veneer and Strip Composite Construction 277
Evenly spaced
mold stations
Plywood or particle
board mold frames
Strongback
Typical canoe mold
Align and plumb
frame centerlines
Stem to become
part of hull
Figure 23-17 A typical canoe mold with plywood frames.
book. If you have any problems finding a book on the
subject, please call us for sources. <strong>The</strong> following brief
outline presents one of the many variations on the
technique.
Setting up for a stripper canoe is not much different
from setting up for a strip plank hull. You can use a
standard four-sided strongback, but a three-sided,
U-shaped foundation made of two 2" � 4"s (38mm �
89mm) and one 2" � 6" (38mm � 140mm) is strong
enough for a 17' (5m) canoe. Set up mold frames and
stems to define the hull shape and bolt them to the
strongback. Fair the set-up and then tape the edges of
the frames or cover them with plastic strips so that they
will not be bonded to the hull.
Many strippers are planked with Western red cedar
and sheathed, inside and out, with 4 oz (135g/m2 ) or
6oz (200g/m2 ) fiberglass cloth. One of the most efficient
ways to prepare stock for planking is to buy nominally
3 1 3 ⁄4" thick flat grain boards, rip them to ⁄4" � ⁄4"
(6mm � 18mm) edge grain strips, and then scarf
them to length.
Canoe designs vary, but it is fairly safe to say that less
than 50% of the planks will need to be full length.
However, additional full-length planks will allow you to
be selective in choosing planks for contrasting grain and
color.
Prior to beginning, you need to decide on a plank
layout scheme, as shown in Figure 23-2. Most canoes
are built using the master plank method, but some
designs are better suited for the double run method.
Each method has advantages and disadvantages with
the double run method requiring fewer fitted joints.
Edge glue the planks with a thickened low-density
epoxy mixture and use staples for temporary pressure
until the epoxy cures. Wire brads or finish nails can be
used at the stations. <strong>The</strong> flat bottom section of a canoe
resembles a football.
Remove staples and nails when the epoxy has cured.
Fair the canoe, first with a block plane and then with
an 11" (280mm) long sanding block. When you are
satisfied, clean the surface with a vacuum cleaner and
wipe the hull down sparingly with warm water and a
sponge. This causes the damaged wood fibers at the
staples and nails to swell and “heal” the holes to a
surprising degree. Allow 24 hours drying under good
dry conditions before applying an initial coating of
WEST SYSTEM epoxy. We recommend using the 207
Special Coating Hardener on strip canoes as it is formulated
for maximum long-term clarity. Allow this initial
coat to cure, lightly sand and clean the surface again,
and apply 4 oz (135 g/m2 ) or 6 oz (200 g/m2 ) woven
fiberglass cloth.
Use the dry method to apply the cloth. (See Chapter 13.)
Fit and cut the cloth and place it over the entire hull
exterior. <strong>The</strong>n follow the special instructions for fiberglass
application for clear finishing presented in
Chapter 13. Use a stiff bristled brush to spread the
epoxy. Use minimal strokes and allow the epoxy to sink
into the fabric. Draw off excess epoxy with a plastic or
rubber spreader. <strong>The</strong> glass at this point should be clear
but slightly dull.
If you want a second layer of fiberglass, you can apply it
one of two ways. You can either let the first fiberglass
layer cure before continuing or apply the second layer
while the initial glass/epoxy layer is uncured. If you let
it cure, prepare the surface with a water wash and light
sanding. Use the same fiberglass wet-out technique on
this second layer. If you plan to continue glassing with
the second layer while the first layer is uncured, it helps
to have an assistant to help you carefully place the
fiberglass. It will be difficult to work out wrinkles so
accurate initial placement is important. Ideally, you
should apply additional coats of epoxy to fill the weave