The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 19 – Keels, Stems, and Sheer Clamps 217
In any boat the scantlings and design of the sheer
joint depend on several factors:
1. <strong>The</strong> displacement of the boat.
2. <strong>The</strong> probable stresses the sheer as a whole (or in
part) will be subjected to.
3. <strong>The</strong> design of the framing system for the entire hull.
4. In the epoxy bonded boat, a careful balance of the
grain strength of the woods used and the bonding
area of the joint.
Dowels
resist
splitting
forces.
Bulkheads or gusseted
frames significantly
increase the strength
of the sheer joint.
Figure 19-12 Considerations in the design of a sheer clamp.
clamp at about right angles to the floor.) If there is severe
twist in the sheer clamp, you may have to brace up the
mold frame to keep it from distorting.
It’s fairly easy to control unusually severe twist in a sheer
clamp by clamping a large stick perpendicular to it. This
gives you leverage on the sheer clamp. You can block
the outside end of the stick up or down to position the
sheer clamp at the desired twist, thereby removing a
great deal of stress from the mold frame. When the sheer
clamp lamination is completed, plane and sand all of its
interior surfaces and apply two or more coats of WEST
Figure 19-13 A sheer clamp laminated on the outside of a
hull, using the hull as a mold. Note the clamping pad on the
outside to protect the cedar planking.
SYSTEM epoxy. <strong>The</strong>n notch the mold frames and install
the sheer clamp in the set-up, following the procedures
described for installing keels.
With the stringer-frame and strip plank methods of
laminating hulls, the sheer clamps are usually installed
in the set-up before planking. With the mold method
and sometimes with smaller strip-built boats, sheer
clamps are not generally necessary for hull construction
and you can install them later, when the hull is
completed. When you do this, be sure to use wood
clamping pads to prevent damage to the hull.