Building the Ultimate Expedition Kayak
Sealing and Fiberglassing
Finally, the day of reckoning had arrived: After all of the aligning and stripping and planing and sanding and filling, it was almost time to fiberglass. For better or worse, my mistakes would be sealed (literally) beneath a sheet of glass and epoxyimmortalized for all to see. There would be no going back. It was time to commit. Time to fight off the nagging urge to smooth this curve or shape that contour. My "work in progress" would officially become a "hull" and show its true colors. Naturally, I was nervous.
There is a wealth of available literature on various fiberglassing techniques, but despite the best efforts of all of them, fiberglassing remains as much art as it is science. Most writers on the subject will tell you that it's important to work in small batches of epoxy (four to six ounces at a time), and to spread it evenly over the glass, working your way from somewhere in the middle of the boat toward the ends, taking care to avoid bubbles and runs and floating glass along the way. It sounds straightforward and methodic, especially since each step of the process is often accompanied by time estimates and tips. But when you finally work up the courage and try it for yourself, it still feels like learning to swim by diving off the deep end of the pool. At least it did to me.
But don't let me scare you. Despite the swimming (or drowning) metaphor, it's not difficult to get good results with fiberglass as long as you take your time. Of course, this means taking a few precautions before you actually begin. Most basic epoxies are formulated to set up at room temperature (about 70 degrees Fahrenheit). The Raka 127 resin and 350 non-blush hardener I had decided upon were no exception. But since the weather was regularly dropping into the low 40s and high 30s with talk of snow, I set up two oil-filled portable heat radiators in the garage to raise the air temperature to the recommended warmth. For the same reason, I also allowed the bottles of epoxy resin and hardener to acclimate to the higher temperature.
In order to safeguard against getting dust embedded in the coats of epoxy, I swept and vaccuumed the garage and then stapled plastic drop-cloth to the ceiling (covering the lights) to keep any additional dust from sifting down onto the boat. I had heard that flourescent lights can sometimes drop dust because they vibrate when they're running, but Bryan just laughed at me and told me I was being way too careful. Maybe I was being laughably cautious, but since a drop-cloth only costs 96 cents and takes less than two minutes to hang with staples, I figured there was no reason not to do itjust to be safe. Since some epoxy was sure to drip onto the floor, I also put down another drop-cloth to make it easier to clean up afterward. And finally, I made sure to lay out several empty mixing cups, a few new plastic spreaders, a couple of brushes, a box of latex gloves, the bottles of epoxy and hardener, and a can of acetone (for cleaning brushes, shoes, etc.). This way, everything would be in easy reach when it was needed.
With the preparations complete, it was time to begin. I had heard that fiberglassing is generally easier if you seal the wood first with a layer of epoxy. If you don't, the wood can absorb epoxy and "starve" the fiberglass during the process of wetting it out, making it difficult to get a clear wet-out. Hoping to make the process go as smoothly as possible, I decided this was probably good advice. So, donning our respirators, Bryan and I mixed up a batch of epoxy and sealed the hull from end to end. It was thrilling to see the rich, dark colors of the wood finally come out. I had been disappointed that the hull seemed to lighten significantly after planing and sanding, but now, saturated with epoxy, it took on a beautiful dark chocolate color. The sealing process took about 30 minutes, and postponed the actual fiberglassing process for at least four hours (until the seal coat finished setting up), but the extra effort and time commitment were well worth it. Aside from whatever ease it may have contributed to the rest of the process, the seal coat gave me an excellent, reassuring opportunity to familiarize myself with the properties of the epoxy before working with any actual fiberglass. For this reason, I definitely recommend doing a seal coat if you're not already an experienced fiberglasser.
Since I wanted a strong, but lightweight lay-up, I opted to use a tight-woven 5 oz. fiberglass instead of the standard 6 oz. fiberglass most kayak builders use. According to Raka, the tight weave of the 5 oz. glass makes it as strong as 6 oz. standard-weave, but prevents it from absorbing quite as much epoxy. Thus, in theory, it produces a stronger, but lighter boat. Since theory is all I had to work with, I decided to trust Raka's input and put one full layer of 5 oz. glass on the hull, with one additional layer of 5 oz. glass covering the "football"the bottom area of the hull, where it is most likely to get banged, scratched, and otherwise abused. The folks at Raka had warned me the tight weave of the 5 oz. glass would require a little more effort and patience to wet out clear, so on top of sealing the wood, I also decided to wet out the glass one layer at a time. It was very lucky that I did. Within 30 seconds of starting to wet out the first layer, Bryan announced that it was "ten times harder to wet out" than anything else he had ever worked with. I could see why. The epoxy pooled on top of it, but barely soaked in without working it with the plastic spreader. Even after the glass started to absorb the epoxy, it took a lot of diligence and persistence to finally wet it out to perfect or near-perfect clarity. In the end, it took Bryan and I two and a half hours of continuous work to wet out the first layeralmost three times longer than normal.
Another four hours later, when the first layer had dried to a mild tackiness, we returend to the garage again to add the extra patch over the "football"area. Despite its smaller size, it still took another hour and 45 minutes to wet out this second layer. In part, this was due to the fraying edges all around the patch, which kept wanting to unravel into the the epoxy and spread awkwardly. For awhile, Bryan and I diligently cut each stray strand and plucked it from the epoxy. But after 20 minutes of this, our patience wore thin and we decided to ignore the smaller strands and just sand them out later. In retrospect, this was a wise decision, as the weave would probably just have kept unraveling the more we tugged and snipped at it. Besides, there were bound to be a few runs in the epoxy that would need sanding anyway. There was no sense stressing about getting it all "perfect" at this point.
About six hours later, I returned to put on the first fill-coat of epoxy. While the wetting-out process focused on getting the fiberglass to wet out fully clear, the subsequent fill coats were intended to fill in the weave until the "textured" look vanished completely and became as smooth as glass. Despite this objective, it's not wise to try to fill the entire weave in one coat. If you do, you risk putting on too much epoxy and getting more runs. It's best to just add a light layer of epoxy, let it set, and add more fill-coats as needed. I mixed up about three batches of epoxy to do the first fill coat, but still ended up putting on a bit more than necessary because I did end up with a few runs in the epoxy that I had to squeegee off again. A 2-inch brush seems to work best for the fill coats because it moves and holds the epoxy better than just pushing it around with a plastic spreader. I worked the epoxy into the weave by drawing X's with the brush back and forth over the weave, and then finishing with a side-to-side stroke that smoothed the epoxy parrallel to the wood grain. It took about 40 minutes to do the first fill coat, and when I came back the next day, it took about 20 more minutes to do the second. By the end of the second coat, the weave had disappeared completely, but I also had added a few runs of epoxy to the otherwise glass-clear finish. More runs means more sanding, but it's not the end of the world. Even so, it's best if you don't get too carried away with the fill coats. Patience at this stage of the process will save you labor later. If you have to, there's nothing wrong with doing three or four fill coats before the weave is filled. Just take your time and try not to oversaturate the glass or spread the epoxy too thickly.
All in all, my first attempt at fiberglassing went very well. I have some sanding to do on the hull to smooth the finish, but the weave is almost entirely clear and invisible, and the colors of the hull are rich and beautiful. I don't think I would recommend the 5 oz. glass to an inexperienced fiberglasser because it is difficult to wet out. Even my thoroughly-experienced assistant Bryan called it "a real pain in the ass." Having said that, I like it and might consider using it again because despite its stubborn wet-out properties, it does look to be very tough and light. Only time will tell. In the meantime, I can only stand here, staring at my newly-fiberglassed hull, feeling a thrill of accomplishment and a sense of excitement in the air. Soon, after the epoxy has set, I will be able to flip the hull over and start building the deck!
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Copyright © 2004, Wesley Kisting