KNOW-HOW - Soundings Online


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It doesn’t matter whether you purchased your boat new, or from whom you purchased it, or who designed and built her. After a year or so you’ll recognize that there are things on deck that are missing or that would work better if they were repositioned.

The first thing to consider is how your boat was built. Most boats built within the last couple of decades have decks cored with end-grain balsa wood or some sort of stiffening material, such as Airex, Klegecell or Nomex honeycomb. Balsa and some of the other coring materials have limitations in providing the structural integrity to support hardware that will be loaded when used. You must provide that structural integrity before installing deck hardware.

Many boatbuilders incorporate pads into the deck and cabin structure to accommodate the installation of hardware. The problem is they don’t always place them where you might want them. All too often, no thought has been given to the installation of midship cleats and chocks, windlasses, capstans, and additional winches, stoppers, tracks or pad eyes.

1.Before you do anything involving fiberglass work commit this mantra to memory: wipe, grind (or sand), wipe. Wipe the surface to be worked on with a solvent, such as MEK (methyl ethyl ketone), Interlux 202, Petit 120, acetone or a similar product that will not leave a residue, and will remove waxes and other contaminants. (Unless it’s a very small area, acetone evaporates too rapidly to permit cleaning before it’s gone.) If you sand first you’ll sand the contaminants into the scratches and never get them out — and never get proper adhesion to that surface.

2. To install deck hardware in a cored structure you must first remove the core material. This usually means cutting out the outer skin of gelcoat and fiberglass.

3. Protect the remaining core material by creating a bevel or fillet, and fiberglassing the exposed core to bond with the remaining skin. The reason for the fillet is that fiberglass won’t adhere to interior or exterior right angles.

4. The strongest way of supporting the hardware you’re installing is to glass in what’s known as a “Dutchman,” a block of wood extending a couple of inches in all directions beyond the footprint of the item. Bed it in a slurry of epoxy and highdensity filler or colloidal silica with a consistency of mayonnaise. After the cure, fix the block in place by through-bolting with flat-head machine screws. (For more detail read the Gougeon manuals on using WEST SYSTEM epoxy, or those of other manufacturers, such as MAS or Interlux. The WEST catalog is free and is loaded with information.) The principle is the same for polyester resins, but they don’t provide adhesion that’s as powerful and aren’t structurally as strong.

5. Glass, gelcoat or paint over the base and install the hardware.

6. When through-bolting the hardware use a backing plate of wood or metal (use washers under the nuts with wood) that extends at least an inch beyond the base to spread the loads the hardware may impose. Next, put a bead of polysulfide caulk around the drill holes in the base you built and under the bolt heads. Hold the bolt head stationary and tighten the nut until the caulk just starts to squeeze out. Once the caulk has cured, tighten the nut all the way, again holding the bolt head stationary. You’ll have created a gasket that is watertight.

7. Another way is to lay up fiberglass or high density filler to fill the void created by the removal of coring. The use of backing plates and the through-bolting technique still apply. I just don’t think this method is as strong.