Wooden Boat Restoration Repair - WEST SYSTEM Epoxy

3. Wet out the lower end of the stud and work thickened epoxy into the threads to avoid
air voids around the stud. Push the coated stud into the epoxy filled hole. A small
amount of epoxy should squeeze out around the nut. Allow the epoxy to cure
thoroughly before tightening the nuts (Figure 6-4). The top of the nut should be barely
above the surface. This helps to reduce the creep load on the epoxy when the hardware
item is tightened down.
6.5 Removable hardware
Testing at Gougeon Brothers, Inc. has shown that with bonded fasteners (screws, bolts,
threaded rods, etc.), the adhesive bond to the metal is not as important as the “keying”
between the epoxy and the threads of the fastener. This factor allows the builder to
coat the fastener with a thin film of mold release before bonding to permit easy fastener
removal after the epoxy cures.
Fatigue tests of bonded threaded rods with and without a thin coating of mold release
show only a 4-10% reduction in the overall fatigue strength of the fastener with mold
release. A thin film mold release will yield a more predictable performance than a thick
film. Mold release may include paste wax, non-stick cooking spray, silicone spray or
hair spray. While the reduction in strength of the fastener treated with mold release is
slight, it should be taken into account when calculating hardware loads. We
recommend adhesive bonding to all hardware and fasteners rather than the use of mold
release whenever possible.
6.6 Removing bonded hardware
Installing Hardware 47
Occasionally it is necessary to remove bonded hardware items. At temperatures above
150°F (66°C), cured epoxy begins to lose its physical properties; the resin softens and
its bonding capacity is reduced considerably. You can use this characteristic to your
advantage when you would like to remove a piece of bonded hardware.
1. Remove all fasteners. If you used a release agent on them when you bonded the piece in
place, they should come loose without too much difficulty. If the fasteners were
bonded in, it will be necessary to apply heat to them, using a soldering iron. The epoxy
around the fastener will soften enough to loosen the fastener when enough heat is
conducted down the fastener.
2. Heat the fitting briefly with a propane torch. Protect the area around the fitting from
heat damage by covering with water-soaked plywood. Allow the heat to conduct
through the base of the hardware. A sharp rap with a mallet should be enough to
dislodge the hardware. If the fitting doesn’t break loose easily the first time, don’t force
it. Heat it a second time with the torch and try again.
3. Replace the hardware by following the procedures in Section 6.2. Re-drill the fastener
holes in the existing epoxy as you would for a new installation.
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