To bed deck hardware, a boatyard worker suggests gluing small pieces of formica to the deck area that will be covered by the hardware then applying the bedding compound to the hardware, and mounting it. This prevents the hardware from squeezing out the sealant when the fasteners are torqued. What is your opinion about this procedure?
Don Casey responds:
The procedure you describe has merit, but it only addresses half of the reason to make bedding a two-step process. Small dots of Formica should indeed prevent you from getting a "dry" joint from squeezing the hardware against the deck. This makes it more likely that, at least initially, the joint will be watertight.
The problem is that when (not if) the sealant loses its grip on either surface, it will leak. However, if after the bedding cures, you tighten the fasteners to put the polymer sealant under compression, you have created a gasket. You might tear loose the sealant under a stanchion base when you haul yourself aboard with the top of that stanchion—and if there is water on deck, it could leak at that moment. But as soon as you release your pull on the stanchion, it compresses against the sealant/gasket, reestablishing the seal.
Replacing the Formica with, say, small squares snipped from a rubber band might be a way to get a predetermined thickness of sealant under the hardware, while still allowing the sealant to be put under compression after it cures.