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October 08, 2007

Laying It Up

Boatbuilding basics from gelcoat to deck

Boats are mysterious creatures. We love 'em, we buy 'em, but do we really understand 'em?

Most of us just knit our brows knowingly as a dealer describes a poured-ceramic transom or a Prisma pre-form stringer system. We smile, nod. Under our breaths we mumble: "Jeez, why do I need a college degree to understand this nonsense?"

The good news is you don't ? really. The key lies in avoiding the terminology. Once you have a basic idea of what comprises the generic fiberglass hull and deck, you can dig a little deeper. Suddenly, the terms no longer swirl about your head like flies at a picnic. You look past the words and grasp the concept. Here's what I mean.

A Layer Cake
When I think about my boat's hull as a layer cake, I can easily picture its makeup. (I also find food analogies very appealing.)

The icing is the gelcoat, a sprayed-on substance - in this case, a resin with added pigment and UV stabilizers - that makes the boat look bright and colorful. Builders spray the gelcoat into a pre-made mold (think Bundt cake pan or something similar, though shaped more like a boat.)

Under the icing - or gelcoat - the first cake layer has a slight outer coat to it. If you've ever baked a cake or seen one come out of the oven,  you know that browned top layer is thin as skin. That's similar to a boat's skin coat.

The skin coat quite often is composed of chopped-up fiberglass and resin. A worker feeds a fiberglass strand from a bale into a "gun" that chops the glass into strands, mixes it with resin and then shoots it into the gelcoated mold.

That skin coat helps create a wall between the more porous gelcoat and the interior layers of fiberglass. A resin-saturated skin coat keeps water from reaching the fiberglass and keeps the fiberglass material from printing through the gelcoat.

Under the skin coat, builders put down multiple layers of resin-soaked fiberglass, just like layers of cake and icing. Because this cake needs more rigidity than a real baked good, workers install a system of foam-and-fiberglass stringers, or beams, which provide   longitudinal and usually latitudinal strength. The foam transom is then attached with putty to the aft wall of the hull and covered with fiberglass.

That's the basic and generic idea. Now, let's look a little more closely at those ingredients and see how various boats might differ.