Saturday, April 11, 2009

Fairing complete. Let's lay some glass!

Fiberglassing the hull is one of the most nerve-wracking (to me, anyway) things to do in the building process. Mainly this is because once started, you have to finish; can't stop until the last coat of epoxy is laid. My concern is that I will get started and find something that I didn't do. I really need to learn to trust my abilities and instincts and. That said, the process is relatively straightforward.

Once the hull is faired and filled, the hull gets sanded with 80 and then 120 grit sandpaper. The 80 grit sanding provides an initial fairing and then the hull gets wetted down with water. The water raises the fibers of the wood that have been mashed down by the scraping and initial 80 grit sanding. Then the final sanding with 120 knocks off the fuzz and provides a good, smooth surface for the glass to adhere to.

Next up, the fiberglass cloth (60z cloth, 60" width and about a foot longer than the canoe) gets laid over the hull. It looks like a sheet draped over it. The glass must overhang all edges at the sheer and the stems.

With the cloth in place, the epoxy gets mixed and brushed on. In brushing the epoxy, enough of the epoxy needs to be applied to soak into the wood and completely saturate the cloth in order to create a good bond. It's important to not leave areas starved of epoxy, as this will either show up as a blemish on the completed hull, and will create weak spots. I don't worry about using too much epoxy at this stage. Runs don't bother me here because they will be taken care of with the squeegee coming later.

Application of the epoxy requires two people (in my shop). I apply the epoxy and my assistant (oldest son) mixes and watches the time for me. Starting at the keel line near one end, I apply epoxy from keel to sheer all the way to the stem on one side; about two feet of the hull. Then I do the same bit on the other side. This anchors the cloth to the hull for the remainder of the epoxying.

Continuing down the hull about two feet at a time, keel to sheer, wet edge first, and side to side, I continue to apply epoxy. I skip back and forth to always overlap the wet edge to ensure the best possible bond.

After about 20-25 minutes, my son tells me to go back and start squeegeeing. At this point, the first section that I applied has begun to set and get a little firm. I use a plastic squeegee (the type used in auto body repair to apply and smooth body filler) and scrape off excess epoxy (and those runs I allowed) and smooth the whole bit. Care has to be exercised to not take too much of the epoxy off which would starve those areas and cause blemishes, but I have to take enough that the glass/epoxy is smooth.

I will continue to work in this way- side to side, spread and squeegee- along the entire hull until the whole thing is epoxied and smoothed from stem to stem, and then it's time to wait. Once the first coat is applied, it will be about 3 hours (depending on temperature and humidity) until the next coat can be applied. I apply three coats of epoxy to the outside of the hull. The first coat adheres the glass cloth to the wood, the second coat fills the weave of the cloth (mostly) and the third completely covers the cloth so that it can be sanded smooth for a final finish of varnish. All three coats are necessary so that when you do that final sanding you don't sand into the cloth. If you sand into the cloth, it will show as a white blemish and potentially weaken the hull in that area.

After the third coat is applied, I like to give it a day or two to cure and then I can turn the hull upright for the first time. This is really exciting for me because it's the first time that it actually looks like a canoe. Once it's turned upright, fairing can begin for the inside in preparation for the 'glass on the inside.

You can see a more detailed series of pictures of fiberglassing a canoe (where I am glassing another canoe) here.

No comments:

Post a Comment