The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

148 Core Boatbuilding Techniques
epoxy-protected surfaces, allowing water to seep
harmlessly between them.
<strong>The</strong> lead surface itself should already be fairly clean,
but a light sanding with some sandpaper will expose
fresh metal for good bonding with the epoxy. <strong>The</strong>
mating surfaces are now ready for a final fitting. <strong>The</strong>
only thing left to do is to establish some reference
measuring points to ensure that the keel itself is indeed
in perfect position with the hull before any epoxy
cures. Proper preparation should help ensure the keel
will settle in an accurate fore-and-aft position when the
hull is set flush upon it, but sometimes a keel, rather
than sitting perfectly true with a hull athwartship, will
favor one side or the other. If you have accurate waterlines
inscribed on the hull, you can take measurements
from these points a set distance aft on either side down
to the very bottom of the keel and adjust the hull so
that this dimension is the same on either side.
<strong>The</strong> final setting of the keel requires the coordinated
efforts of several people. Make up enough epoxy
mixture at one time to cover the entire bonding surface
of the keel, using equal proportions of 406 Colloidal
Silica and 404 High-Density Filler. You need enough
thickened epoxy to be sure that no gaps will remain
anywhere between the hull and the keel, a quantity
sometimes so large that two or three people mix
separate pots simultaneously. <strong>The</strong> mixture should be
so thick that it will not run.
Liberally spread it over the entire mating surface.
Lightly coat the bottom of the hull. Remember,
however, that you begin to work with a time handicap
the moment you apply the adhesive. <strong>The</strong> hull must be
set down on the keel and trued up before the epoxy
cures. In most situations, this means that you have
from 20 minutes to 1 hour for the operation. If you
are well prepared, this should present no problems.
When the hull is in final position, excess epoxy will
squeeze out of the keel/hull joint. If the mixture is as
thick as it should be, it will not run down the sides of
the keel. Remove the excess and use it to make a fillet
between the keel and the hull if desired. Use solvent
and paper towels to clean up any leftover adhesive on
either the keel or the hull.
When the epoxy between the hull and the keel has
cured, begin the second stage of bonding the keel.
Use a syringe to fill each keel bolt hole to the top
with unthickened epoxy. Feed each hole continually
because large amounts will soak into the significant
wood surface area in the hole. As you do this, it
sometimes helps to run a piece of wire up and down
around the keel bolts to help remove air bubbles and
trapped air. When this epoxy cures, install washers and
nuts to complete the keel.
Removable Bonded Keels
<strong>The</strong> biggest problem with bonded keels is removing
them. Bonded keel bolts can be extracted, but with
difficulty. If for some reason you decide to remove a
bonded keel, try using a cutter made from steel tubing,
which passes outside of the keel bolts.
If you plan to remove a keel on a regular basis for
shipping or trailering, use the following alternate keel
assembly technique. Instead of attaching bolts to wood
fiber, thread or groove the exterior surfaces of sections
of stainless steel pipe. Fasten the keel bolts through
these sleeves, as shown in Figure 14-26. <strong>The</strong> bonded
pipe transmits keel load through a large surface area.
With a little modification, this basic idea can be used
to attach other removable through-hull fittings.
Cut Off Hole Saw
Steel Conduit
Threaded Rod
Weld and grind
smooth
Grind threads
to form a
smooth shank
Figure 14-25 A custom keel bolt cutter can be made from
steel tubing and a standard hole saw.