The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 14 – Hardware Bonding 145
achieve optimum load distribution, begin preparing for
keel installation. Do this well in advance so that when
the time comes, the task of joining the keel and the hull
can be accomplished with the least amount of grief.
Pour the keel as soon as possible so that you will have
plenty of time to prepare it for final installation. Clean
the casting and then rough up its surface with a wire
brush to remove oxidation. Coat the keel with epoxy
and, while the epoxy is still wet, scrub it again with
the wire brush. WEST SYSTEM epoxy bonds well to clean
lead surfaces. This coating will improve both paint
adhesion and the interface between the high-density
lead and lower density epoxy, and it will also reduce
immediate oxidation. Fair the top of the keel where it
will meet the hull. If it’s very heavy, you may want to
build a special fixture for the keel so that you can roll
it around the shop. (See Figures 14-23 and 14-24.)
By far the easiest way to install bolts in a keel is to put
them in a temporary fixture and pour the lead around
them as the keel is made. When the bolts are in place,
check them for dimensional accuracy. <strong>The</strong>y must be
perpendicular to the bonding surface of the keel and
each must be parallel, both fore and aft and sideways,
to the others.
Centerline of ballast keel
marked on the pattern
Scrap plywood
Plywood pads with holes drilled to the
diameter of the keel bolts are dropped
over the bolts and stapled to the main
piece of the pattern
Oversize holes in
plywood
Lead Keel
Figure 14-21 Making a pattern of the keel bolt locations that
can be transferred to the keel for drilling.
<strong>The</strong> next step is make a pattern which sits on the top
of the keel, as in Figure 14-21, to accurately record the
locations of the individual bolts so that you can transfer
them to the hull and drill holes to receive the bolts. For
this, you will need a sheet of plywood at least as long
and as wide as the top of the keel. Mark the pattern
with an accurate fore and aft position for the keel so
that when you line it up on the hull, the centerlines
of the keel and hull line up. <strong>The</strong>n set it on top of the
bolts. Line up the pattern and mark the locations of
each keel bolt. Rough cut bolt holes, allowing a wide
margin around each one so that the pattern drops easily
onto the top of the keel. Push it down until it lies flush.
When this is done, make small square or round
plywood pads for every bolt and drill the exact keel
bolt hole diameter in the center of each piece. Slip a
pad over each bolt, centering holes around the bolts,
and staple in place. <strong>The</strong>n ask several people to help
you lift the pattern straight up and off the keel. If it
catches on misaligned bolts, bend them as necessary.
Correct any misalignment now; interference fits from
out-of-parallel bolts can cause a great deal of trouble
when the keel is installed.
If you haven’t yet installed laminated floor timbers, use
this keel pattern and the existing keel bolt arrangement
as guides to do the job more accurately. If the floor
timbers are already in place, adjust the pattern so that
the bolts pass through all of them to best advantage.
Position the plywood pattern carefully on the centerline
and mark the bolt holes carefully on the floors or
keelson.
Determine the diameter of the holes through the floors
before you start drilling. <strong>The</strong> hole diameter should be a
least 1 ⁄8" (3mm) larger than the keel bolt. An important
limitation on hole size is the size of each laminated
floor timber. A larger oversize hole will distribute load
over more surface area, but if you remove too much
material, the floor timber may be weakened. Balance
the surface area needed for load distribution against the
dimensions of the floor timbers before making a final
decision on hole size.
<strong>The</strong>re are both advantages and disadvantages to
increasing the diameter of an oversize hole. It’s very
difficult to maintain even 1 ⁄16" (1mm) tolerances over a
series of holes. If you increase hole diameter, you don’t