-- Last Updated: Nov-06-12 2:09 PM EST --
G Flex is more viscous than other epoxies such as System 3, MAS, or West System 105/205-206. I have found that it wets out 6 oz/yd fiberglass or aramid cloth just fine as long as you are applying only one layer at a time and the working temperature is not too cool. The trick is to be patient and let the cloth take its time taking up the epoxy. Don't be in a rush to force it into the weave. Fortunately, G Flex has a pot life of about 45 minutes at room temperature (longer at cooler temperatures) and an even longer working life so you have time.
Yes, you can warm G Flex and it will reduce the viscosity but it will also reduce the pot life and working life so I would try a couple of other things first. If you have an accessory lamp on a cord put a 100 Watt bulb in it and lay it or hang it under the part of the hull you are working on several hours before you apply your cloth. You might be able to put your space heater underneath the inverted hull if there is a good bit of space between it and the Royalex. Obviously take care to avoid overheating the hull. You can also use a hair drier or heat gun to gently warm the part of the hull you are applying cloth to before you put the cloth on the boat and wet it out.
Fiberglass cuts easily with regular scissors. Aramid does not. I have been successful in cutting aramid cloth with scissors but it does dull the scissors and gives your hand a work out. Some people lay the cloth on a cutting board and use a razor knife to cut it.
All woven cloth will tend to fray as you cut it and wet it out. You will get better at minimizing the fraying as you gain experience. If you are cutting rectangular patches on the warp (along the line of the fibers) be careful to cut exactly along the line of one of the glass fibers to minimize the number of transected fibers that will be susceptible to fraying. Patches cut on the bias actually are less prone to fraying along the edges.
Like a lot of folks, I will cut my patches slightly larger than I want the end result to be and then remove a couple of strands from each side before applying it knowing that they will probably fray anyway. The fibers that are left "sticking out" from the patch are easily sanded off after the epoxy is cured.
As you wet out the cloth start applying your epoxy in the center of the patch and rather slowly progress out to the edges. As you apply epoxy to the cut edge very gently dab it on without dislodging the fibers along the edge and let the fibers take up the epoxy before working that part of the cloth very much. Try not to work the cloth in a direction that separates fibers from the edges of the cloth until the epoxy has become tacky enough to hold the cloth down.
You might find that an inexpensive, disposable, metal handle "acid flux" brush is a good tool for applying the epoxy to the cloth.
It generally takes at least 2, and often 3 applications of epoxy to completely fill the weave of the cloth. With each successive application the cloth will take up progressively less epoxy, however. You might not need to completely fill the weave of the aramid cloth on the inside but you will want to do so on the exterior if you want a smooth surface. At cool temperatures, G Flex may take longer than overnight to cure. If you let the epoxy fully cure before applying another coat then you should either wet sand the cured epoxy or wash and rinse it to remove the amine blush which could interfere with bonding of the fresh epoxy.
I will often feather my patches after the wetting out process before filling the weave of the cloth. As long as the epoxy is cured, or nearly cured, you won't disrupt any fibers in the cloth as long as it was properly wet out. I usually do this by wet sanding with water proof paper using something like 180 or 220 grit. After the cloth weave is completely filled I wet sand again down to maybe 400 grit (or finer).