Wetting out Fiberglass
This tutorial has a video demonstration
Woven fiberglass is very easy to wet out with epoxy. In most boats, the woven cloth will range from 3 to 10 oz. in weight. There are two properties of woven fiberglass which determine how easy it will be to saturate with resin. The first is the weight; heavier glass will need more resin and generally needs to be "worked" with a spreader or roller. The second is the weave style tightness. Due to the weave being very tight, some finish cloths (around 3oz. in weight) can be take more time/effort to wet out than a coarse weave 10oz. cloth.
For wetting out woven tape, our preferred method it to use a 2" chip brush. Do not over load the brush with a lot of resin. Dip the chip brush into the epoxy and "paint" a small section. Even though the area you have just coated will not be completely clear, move on to the next section. As you progress, you see the tape turn transparent - it takes a few minutes to soak into the glass. When you have reached the end of the length of tape, go back and touch up the spots that are not transparent. Woven tape is normally wet out while on the part (not on a table).
Woven cloth is very similar to the tape, just larger in scale. The preferred method of wetting out woven cloth is to first position the cloth on the part. Pour mixed epoxy directly onto the glass. Using either a 6" spreader or foam roller, spread the epoxy to distribute it evenly over the glass. As with the tape it may take a minute for the resin to soak into the glass and go transparent. It is sometimes helpful to brush some resin around the edges of the glass to help keep the cloth in its place. It is possible to use the same 2" chip brush to wet out wide cloth - but this will take MUCH more time and will result in a waste of epoxy.
Biaxial tape and wide cloth:
Biaxial Cloth and tape (without mat) can be wet out using the same techniques as the woven cloth. When using 6 or 12. oz Biaxial tape, you can follow the same procedure as the woven tape. The methods for woven cloth also applies for biaxial cloth up to 17 oz. (without mat)
Biaxial WITH mat, however, takes more work. Biaxial cloth with mat is thick and heavy, which makes it very difficult to wet out effectively from one side with most epoxies. Some very thin laminating epoxies are the exception (like S3 Silver Tip). With most general-purpose epoxies, you will need to wet out the mat side first, flip the glass over and then wet out the biaxial side. For larger parts like the hull bottom, you may need to roll the glass up on a pipe or piece of PVC, then roll it back onto the boat
Wetting cloth on a vertical surface: Wetting out cloth (biaxial or woven) on a vertical surface can be tricky. For lighter cloth simply "paint" some epoxy along the upper edge of the part. For example: On the side panel of a boat, you might paint some resin along the chine. Just a little resin will hold the cloth in place. For heavier Woven and Biaxial it is best to give the whole part a thin coat of resin with a roller. Once the cloth is in place, use a spreader or foam roller to wet out the glass. One trick is to pour some epoxy down the surface of the glass, then with a plastic spreader, catch the drip at the bottom and work it back to the top. Here is a picture of 17 oz biaxial being wet out using this method.