S-Glass Fiberglass Cloth

When E-glass is not strong enough for the weight

S-glass is a different glass chemistry, not a different weave. The same yardage in S-2 glass carries roughly 30 percent more breaking strength and noticeably more stiffness than E-glass of the same weight, which is why it shows up on boards, race hulls, foil parts and anywhere a laminate has to survive impact without getting heavier. The trade is price: expect to pay around twice what the equivalent E cloth costs.

Where it earns its money

S-glass is worth it when weight is the constraint and failure is expensive. A surfboard or SUP deck that has to take heel dents, a kayak hull that gets dragged over rock, a foil fuselage, a repair on a hull that already flexes more than it should. It is not worth it for general sheathing, fairing layers or anything you are going to add thickness to anyway. For those jobs, buy the E-glass and put the savings into more layers.

Genuine S-2, and it says so

Some suppliers sell a heavier E-glass as "S-type" or "high strength". What is on this page is real S-2 glass in the published mill styles: Style 6522 in 4 oz, Style 6533 in 6 oz and Style 6781 in 8.9 oz 8-harness satin, which is the same satin construction as 7781 with the stronger glass. Every listing shows the style number and the dry breaking strength in its specifications so you can check our claim against the mill data rather than take our word for it.

Working with it

S-glass wets out and handles like E-glass, so nothing about your layup changes. Use epoxy to get the full benefit; polyester and vinyl ester will bond fine but will usually be the weak link before the glass is. Widths run narrower than E cloth at 27 and 30 inches, which suits boards and panels more than full hull sheathing.