How to Make a Kayak - Fiberglassing the outside
I tend to drip a lot of epoxy on the floor while I work, so I start by cleaning up whatever crud has accumulated so it does not become petrified. After sweeping the floor, dust off the boat. Any large chips that end up under the fiberglass can cause bubbles and an uneven surface.
Before I start cleaning up I crank up the heat in the shop. I set the thermostat to 90° F (32 C). By the time I get to actually applying epoxy I want everything warmed up. I roll out the glass onto the boat immediately after cleaning up and then leave the shop to give the space, boat, fiberglass and epoxy time to warm up.
The Saturation Coat
The "saturation coat" is where the fiberglass gets saturated with epoxy. I start by turning down the thermostat a bit so the boat is no longer being actively warmed up. I want the temperature steady or falling from now on.
I mixed up a fairly large batch of epoxy. For me, this constitutes about 1/3rd of a large (quart) yogurt container. I immediately dump most of this on the boat, and start spreading it quickly. I am trying to be sure the whole surface get enough resin to saturate the cloth fully. Because the shop is warm the epoxy soaks in fast and the wood absorbs some resin. I would like the surface of the epoxy to be slightly glossy so that any bubbles in the resin are free to rise to the surface above the level of the fabric. After an initial quick pass to get the epoxy spread out fast, I come back with a brush to add epoxy in the drier spots.
Again, with the warm temperature in the shop, I can't leave the excess epoxy too long, but I want to give it some time soak into the wood and let any trapped air escape. I mixed up another batch of epoxy and continued toward one end, then went and started the other end. After finishing off a batch of epoxy I went back to the first areas I added epoxy and squeegeed off the excess resin.
I cut a short vertical slit in a paper cup. This will be my grunge cup. Starting at the center line I drag the squeegee towards the edge. The squeegee is angled slightly with light-to-moderate pressure. The idea is to scrape off excess resin without starving the weave of the fabric. I'm moving fast but not so fast that i create froth while dragging the squeegee. After each pull of the squeegee, I run its edge through the slit cut in the cup to remove the resin I picked up. I only worked on the area where I applied the first batch of epoxy.
After scraping the first area, I went back and continued saturating the remaining boat. After each batch I go back and squeegee the next un-squeegeed area.
Since I have forms for both the deck and hull, I continue directly on to the hull. My camera battery died partway through the hull, but it proceeded as described above. I have not installed an outer stem yet, so I did not need to wrap the fiberglass tightly around the stems.
After I finish the squeegee work I turned down the temperature some more and left the shop for a few hours
First Fill Coat
When the epoxy had started to set up and was adhering well to the boat, but still sticky I applied a fill coat. For this coat I wanted to fill the weave a bit and force epoxy into any low spots. Again, I spread on too much epoxy then sgueegeed off the excess into a grunge cup. At this point the goal is to just start filling the texture, not obscure it completely.
After squeegeeing I turned down the thermostat again and left the shop for a few hours.
Second Fill Coat
With this coat I am working on obscuring the fabric texture. I use a brush to apply a thick coat of epoxy over the whole boat. Working between the staple marks, one form section at a time, I brush on a heavy load of epoxy, spreading it on with horizontal brush strokes. Without re-dipping the brush I then go over that form section with vertical strokes from center line to sheer line. This is followed by another set of horizontal strokes over the whole section, then I move down one set of forms and repeat with each area between staple marks.
The whole boat should end up shiny with maybe some dust specks and the occasional crater where the staple holes suck up resin. I went over the whole boat with a heat gun. Blowing hot air heats up the surface coat of epoxy, lowering the viscosity slightly and expanding any fine bubbles trapped in the resin. The bubbles rise to the surface and pop.
Once again I turned down the thermostat slightly so the set temperature is about 60° F (15°C)
Third Fill Coat
I let the boat sit over night then repeat the process of the 2nd fill coat to build up the epoxy on the surface. This should give me enough that I won't sand into the glass when I do the finish sanding later in the project. I also went around to add dots of epoxy to fill any craters.