The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

140 Core Boatbuilding Techniques
finish. <strong>The</strong> hardware placement, marking, and drilling
procedures differ from the procedures needed for the
bonding operation. Just gathering together the proper
tools (or materials) for either operation requires considerable
time, and you increase efficiency if you minimize
this unavoidable start-up time.
If you are bonding hardware to a surface that has
received its final paint finish, there is one more step
that you must take before bonding begins. After you
set the hardware in final position, draw a pencil line
around its perimeter. Remove the hardware and apply
tape, usually 2" (50mm) wide, around the perimeter of
the pencil line, overlapping slightly so that the entire
mark is covered. Reposition the hardware, using the
drilled fastener holes as guides, and then carefully cut
through the overlapping tape with a sharp blade, using
the hardware perimeter as a guide. In this process, do
not cut through the epoxy surface. Use only enough
pressure on the blade to cut through the tape. Remove
the hardware and peel away the tape in the bonding
area, leaving a taped outline which perfectly matches
the hardware perimeter. <strong>The</strong> final step is to scrape away
the paint in the bonding area with a sharp edge tool
down to the cured epoxy surface, being careful not to
disturb the taped outline border. You can then proceed
with hardware bonding without getting epoxy on the
painted surface immediately surrounding the hardware
item.
Figure 14-12 Sand the bonding surface of steel and bronze
fittings with coarse sandpaper.
You can prepare the bonding surface area on many
hardware items well before installation. For example,
you can surface treat aluminum items many hours
ahead of actual bonding if you take care that the
bonding surface does not become contaminated.
(Don’t touch the bonding surface.) You can clean with
solvent and sand steel and bronze items ahead of time
(see Figure 14-12). <strong>The</strong>n at installation you need only
coat them with epoxy and re-sand them before bonding
(see Figures 14-13 and 14-14). You should also clean
the cured epoxy surface to which you will bond the
hardware, using a solvent or water. Lightly sand the
surface, especially if it has not been sanded up to
this point.
Next, apply epoxy to the hole. <strong>The</strong> techniques for
doing this vary according to the anticipated loading
on the fitting and the size of the hole. In all cases,
however, a clock starts when you begin to work: the
hardware must be in place before the epoxy in the
fastener holes sets up. Oversize holes can contain
epoxy concentrations high enough to speed up the
exothermic reaction and shorten working time considerably.
In hot weather, even with slow hardener, holes
over 1 ⁄2" (12mm) in diameter may start to gel in 20 to
30 minutes. Plan the installation procedure so that it
can be completed as rapidly as possible.
If you have drilled standard pilot holes or oversize
holes for small fittings that will be loaded in shear,
follow the procedures already discussed for bonding
small fasteners. If you are using coarse machines screws
in oversize holes for heavy duty hardware such as a
winch or mooring cleat, wet out the hole with WEST
SYSTEM epoxy and fill it with a thick mixture of epoxy
and 404 High-Density Filler as described for perpendicular
surfaces. <strong>The</strong>n coat and install the fastener.
When you have filled the fastener holes, coat both the
hardware and the surface to which it will be bonded. If
the surfaces mate perfectly, you can use epoxy with no
additives, but if there are voids or gaps between them,
mix 404 High-Density Filler with the epoxy to desired
viscosity. Apply the mixture to both surfaces, using more
where needed to fill gaps. (Try to visualize the high and
low areas as the fitting is sitting on the bare surface.)
With practice, you can apply the right amount of epoxy
to the hardware, enough that there is reasonable excess