Woven fiberglass cloth fabric is an inorganic composite fabric composed of glass strands of different sizes. After the user applies this material to a surface, he saturates the cloth with polyester or epoxy resin. The resin hardens the fiberglass into a strong, durable substance.
Fiberglass cloth is often used in mold-making, fiberglass repair, and wood reinforcement projects. Lower-weight fiberglass cloth is ideal for waterproofing, while heavier-weight fabrics are often used to increase a laminate thickness. Because UV rays and high temperatures can not damage cured fiberglass laminates, this composite material is ideal for boat construction projects.
Cloth is often classified by how much it weighs per square yard, which also correlates to the thickness of the cloth. Examples include super-light 2 oz. cloth at one end of the spectrum, while extremely heavy 40 oz. the fabric sits at the other end.
Plain-weave fiberglass cloth contains strands that lie at 90-degree angles to each other. This type of weave offers maximum stability but is not very flexible. However, it is easy to cut and manipulate plain-weave cloth, as less prone to unraveling.
Satin-weave cloth has 3 to 7 warp threads with 1 floating fill yarn stitched under a different warp thread. This extremely flexible weave lends itself well to different shapes.
Twill-weave cloth uses a diagonal rib, caused when 1 warp thread lies atop 2 fill yarns. This flexible cloth combines the best points of the plain-weave and satin-weave cloths. However, it can easily unravel once cut into shape.
Your application will determine whether standard fiberglass cloth, woven roving, or mat is the right choice.
Standard fiberglass cloth consists of fiberglass strands blended into a right-angle weave pattern, and is available in different thicknesses. Lighter-weight cloth lends itself well to general repairs and wood surface protection. Heavier-weight fiberglass cloth adds bulk to a multi-layer laminate.
Fiberglass woven roving is a beefed-up, coarse-textured type of fiberglass cloth. It is both stronger and less expensive than standard fiberglass cloth. Fiberglass boat-builders often insert woven roving between fiberglass mat layers in lamination projects.
Woven roving also combines well with chopped strand mat for larger-scale builds. However, woven roving is not meant for high-visibility areas. It is very difficult to hide the coarse weave without large amounts of resin. This is known as print-through.
Fiberglass mat is a low-cost fiberglass product composed of small glass fibers, each 1" to 2" long. A dried binder holds the fibers together within a solid sheet.
Boatbuilders typically use relatively heavy fiberglass mat, also known as CSM or chopped strand mat, to add thickness to a fiberglass laminate. By itself, the mat is not very strong, so it should be used in conjunction with another type of cloth.
Fiberglass varied weights correspond with the materials usage specifications. Cloth weight per square yard ranges from 2 oz. to 40 oz. For boat repair purposes, look for cloth that weighs between 4 oz. and 10 oz. As a guideline, buy cloth that is thick enough to withstand everyday abuse, but light enough to wet out and work into a mold.
4 oz fiberglass cloth is used for a wide range of applications, including canoe and kayak building. For larger areas, 6 oz to 10 oz cloth is preferred.
Cloth that weighs more than 10 oz is harder to wet out and does not handle contours and corners well. Instead, use multiple layers of lightweight cloth to get the desired thicker effect.
Plain weave fiberglass cloth features a right-angle weave pattern, is available in different weaves and thicknesses, with each thickness tailored to specific applications.
Fiberglass mat is made of glass fibers, each from 1 inch to 2 inches long. The fibers are blended into a sheet-like structure with help from a dry resin-infused binder. Mat, or matt, is useful for adding thickness to a laminate, but lacks the strength of cured cloth, and should not be used in structural applications.