To make a void in the foam under the gel coat and laminate layers, you can break down the foam by using a small L-shaped tool, perhaps made from an old Allen wrench or other hardened steel rod. The L-shaped tool is pushed into the hole and manipulated to break down the foam. The tool is withdrawn and the foam debris vacuumed from the hole. This is repeated until a cavity or void in the foam is created around the hole in a suitable width and depth. At some point you may be able to chuck the tool into a variable speed drill or hand power tool and rotate the tool under power. A sketch shows a side view of the process:
- Use a small L-shaped tool as a crude auger to cut away and remove foam under the laminate layer, creating a void or pocket. Into this void a mixture of epoxy and filler can be introduced to create additional material for retaining a screw fastener.
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To introduce resin into this cavity you can use a plastic syringe.
WEST System sells these accessories.
The resin should be mixed with fillers to avoid creating a pocket of pure resin. Epoxy resin is exothermic, and a large volume of pure resin left to cure will become very warm; sometimes so warm that it is quite hot and will tend to melt the foam, creating a "China Syndrome" effect. For this reason, use a resin-filler mixture. The consistency of the mixture can be somewhere between catsup and creamy peanut butter, but with enough viscosity that it can be pushed into the cavity by the syringe. Of course, this works best if gravity is assisting the movement of the resin into the bottom of the void. If you must work against gravity, try to let air escape as you inject the resin mixture, then immediate cover the hole with tape when you pull out the syringe. You can also experiment with adding some thinner resin at the end of the process to better flow into any remaining voids.
The outcome should look like this:
- When the resin cures, it creates a reinforced area into which a new pilot hole can be made, and a new fastener threaded. The resin will spread the load of the fastener over a larger area of the deck laminate.
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Although the process mentioned in the FAQ specifies a hole of a particular diameter (0.5-inch), for this annulus method I would not enlarge the original fastener hole any more than necessary to eliminate the old, broken down laminate. With care I think you can easily create an annulus of at least 0.5-inch width or more, as you think necessary. The FAQ method refers to securing rail bases which have a rather wide base around them and their mounting holes, so the open 0.5-inch hole that is created is mostly or completely covered by the rail base. With the annulus method the hole needs only to be large enough to remove any fractured laminate and to permit the L-shaped tool to be inserted.
Always relieve the gel coat layer of the hole so the threads of the fastener are not forcing the gel coat layer apart; the gel coat is brittle and can easily fracture if you try to force a screw fastener threads into it.