The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 25 – Compounded Plywood Construction 297
Figure 25-6 Tornado catamaran hull panels are held at the
correct angle with notched sticks and a plywood form.
them. In the bow area, for example, we may work
towards an 80° keel angle, while in the midsection we
might want an angle of 140°, and perhaps even 160°
toward the transom. Three checking stations seem to be
accurate for boats up to about 30' (9m) long.
One way to make sure that the two panels meet at the
desired angle is build a simple jig or temporary frame
support. (See Figure 25-7.) This clamps to the exterior
part of the hull and forces the two panels into the exact
position you want. If you have three checking stations,
make up three jigs, one for each position. Often,
plywood doesn’t lie flat as it is spread. Instead, it curls
slightly inward and a straightedge shows a hollow on
the outside of the panel. This means that if your jig is
set for 120°, the plywood at the keel may only be
spread to 110°. <strong>The</strong> solution is to spread the sheers
further than 120° apart until the panels are at the
correct angle at the keel. Remember that the permanent
joint will be made at the keel, and it is only this angle
which is crucial at this stage.
When the two panels are spread to desired angles,
begin tightening the wires, if you are using them, until
the edges are drawn tightly together and centered with
a relatively straight keel line. If you have used webbing
along the keel line, this step is eliminated. At this stage,
Figure 25-7 Panels for a trimaran outrigger hull showing
temporary frame supports.
wires may tend to pull away from each other at the keel
line and leave gaps of up to 3 ⁄8" (9mm). Lightly tap each
wire with a sharp tool and drive it into a V in the joint.
As you do this, try to put your tool exactly in the
middle of the wire between the two panels because an
exact, accurate V promotes good alignment when you
pull the pieces together. Twist each wire again until the
edges are snug at the keel line.
During the tightening process, if one edge of a panel
seems a little higher than the other, use finger or thumb
pressure to hold the edges in alignment until they butt
Plywood panels spread out to designed angle
Tighten loose wires by pushing
down on the center here
Figure 25-8 Tightening wires at the keel joint.
or
Tighten by further
twisting here