52 products

Fiberglass

Picking the right glass for the job

Weight and weave decide the job. Light E cloth (3, 4, 6 oz) is for skins, sheathing and cosmetic layers where you want the weave to disappear. Chopped strand mat (0.75, 1.5, 2 oz) has no directional strength but bulks a laminate and ties woven plies together under polyester.

1708 is 17 oz biaxial with a mat backer, which is why it is the default for transoms and stringers; DB170 is the same 17 oz biaxial with no mat, for epoxy work. Widths run 30, 38 and 50 in, in 1, 3, 5 and 10 yard cuts. Tapes from 1 in to 6 in save cutting strips off a wide roll for a seam or a chine.

Fiberglass cloth is woven for strength in specific directions, while chopped strand mat is made of randomly oriented fibers and is better for building bulk.

Unlike woven cloth, biaxial fiberglass is stitched, not woven, so it lays flatter, wets out faster, and provides superior load distribution without crimped fibers.

Woven roving is much thicker and heavier than standard fiberglass cloth. It’s used for strength and bulk, while cloth is typically used for finishing or lightweight laminates.

The weight refers to ounces per square yard. Lighter cloth (e.g., 4oz) is more flexible and used for fine finishing; heavier cloth (e.g., 10oz) provides more strength and bulk.

Fiberglass cloth works with all three marine resins: epoxy, polyester, and vinyl ester. Unlike chopped strand mat, woven cloth has no emulsion binder to dissolve, so it wets out cleanly in any of them. Epoxy gives the strongest, clearest bond and is the standard for wood and structural work, while polyester and vinyl ester are common for production and gelcoat repair.

It depends on the fabric, the area and the number of plies. For hand layup, plan about 0.73 oz of resin per square foot per ply of 6 oz cloth, 1.22 oz for 10 oz cloth, 3.4 oz for 1.5 oz chopped strand mat and 4 oz for 1708 biaxial, then add 15 to 20% for waste. Mat takes about 2.3 times its own weight in resin. The resin calculator works out a full layup.

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