Finally Fiberglassing

The day I dreaded for more than a year arrived earlier this week. After two weeks of sanding, I was finally ready to fiberglass.

Six ounce cloth, pinned into place. The fabic has a nice drape and wrinkles are not a problem.

A close-up of the fabric showing how it meets the edge of the keel.

Applying the first coat.

Now you see it, now you don't. The fabric on the left side turned transparent after the first coat of epoxy.

You might recall that I began preparing for this day nearly six months ago when I practiced fiberglassing the hatch cover and rudder. I quickly learned that fiberglassing, despite its reputation as an alchemist’s art, is relatively straightforward. It is simply the process of adhering a white cloth-like material to plywood with several coats marine epoxy. I am told that this step protects wood with a waterproof membrane, adds some strength, and prevents unsightly checking of douglas fir plywood.

Before beginning work on the hull, I reviewed a wonderfully helpful two minute instructional video produced by West Systems, one of the major epoxy manufacturers. The online video reminded me to place the fiberglass cloth over the bare wood, pour some unthickened epoxy in the center, the gently spread the syrup-like substance over the surface with a rubber paddle, pushing the epoxy toward the edges. The cloth turns nearly transparent as epoxy fills the weave.

In nearly every case, additional coats are recommended to fully fill the weave and leave a smooth surface. It’s possible to wait for the first coat to harden, and then apply a second coat after sanding. That was my strategy with the hatch cover. But the video told me that I could apply the second and third coats after each preceding coat turned about as tacky as masking tape. This produces a stronger bond and eliminates the need for sanding—a real advantage, in my opinion. I hate sanding epoxy. So I set aside the entire day and decided that, come sundown, I would have a fully ‘glassed boat bottom.

Boat builders are an ornery bunch and they can argue over anything and there is an ongoing battle over best weight of fiberglass. It’s possible to buy cloth as thin as fine silk (two or three oz by weight) or as thick as canvas (eight or ten oz). The thinner cloth is lighter and needs less epoxy. However, the heavier fiberglass produces a stronger, more rugged hull. So priorities must be established. Some of us want to build butterflies—spare and elemental; others want tanks—impenetrable and protecting. I can’t help but believe that deeper values and worldviews are being expressed by our choice of cloth.

My choice? In keeping with my personality, I looked for the middle ground and followed the advice of people I know and trust. Chuck Leinweber, editor of Duckworks magazine and merchant of economical boat building supplies, advised me in a series of emails to go as light as possible but add some strength where it counts. His recommendation was six ounce cloth for the bottom, and four ounce cloth for the sides, deck and cockpit. I dutifully complied.
On the appointed day, I began by unrolling fourteen feet of the six ounce fiberglass, laying it along the port side of the boat’s bottom and holding it in place with pushpins spaced every two or three feet. I then trimmed the fabric along the outside edge of the boat, letting it drape over the sides by a couple of inches. I mixed a double batch of epoxy (four squirts of the epoxy, two squirts of hardener) and began the methodical process of adhering the fabric, taking long, firm sweeps across the fabric with my paddle. The goal is to saturate the cloth and avoid bubbles. It sounds tricky, but it’s actually easy work.

When the first coat is finished—five batches in all—I repeated the process on the starboard side. An hour later, I returned to the port side and applied the second coat. This took even less less time and used about half the amount of epoxy. Once again I walked around the boat and did the same thing to the starboard half. Back and forth I went until, by mid afternoon, I had three full coats on both sides.

One part that is not fiberglassed is the boat’s keel. If there is any consensus within the Stevenson boat building community, it is this: Don’t fiberglass the keel, no matter how much you may want to! New builders like the idea of encasing the softwood keel. It makes sense to protect a part of the boat that takes the most abrasion. But experienced builders insist that this actually promotes rot. Water will seep in eventually, get trapped by the fiberglass and do its dirty work. I did paint a thin coat of epoxy over the wood (I couldn’t help myself), but I forced myself to follow the advice of fellow builders and fiberglassed up to, but not over, the keel board.

The only challenge to fiberglassing, as far as I can tell, is learning to apply even coats and avoid drips. In this regard, my skills are poor but improving. The trick, I am learning, is to apply thin coasts. It’s temping to pour on the epoxy in order to get a quick buildup, but this approach almost guarantees a lumpy, uneven finish. The port side was the most uneven; the starboard side was a little better, reflecting the slow evolution of my skills.

I had better luck with the hull sides, which I glassed a couple of days later. For these vertical sides, I couldn’t pour the epoxy over the fabric, so I decided to use a small paint roller. I found that the foam roller easily saturated the cloth, but prevented unnecessary buildup. Each coat went on quickly and, by the end of the day, I felt like an old pro. I hung around for and extra half hour, smoothing out a few drips and sags, but the end result was a surprisingly even finish.

So the step I most feared turned out to be not so bad after all.

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