E-glass vs. S-glass for Surfboards
There are two common types of woven fiberglass cloth used in surfboard construction, E-glass and S-glass (or S-2 glass).
4 oz. E fiberglass cloth is the most common fiberglass cloth used to glass a surfboard. E-glass is easy to wet our with polyester or epoxy resin and laps around the rails easily. If you want the lightest weight surfboard the common layup is 2 layers 4 oz. E-cloth on the deck and 1 layer 4 oz. E-glass on the bottom. Surfboards made with all 4 oz. fiberglass cloth are light but not the strongest...(unless you use S-2 glass, keep reading)
Fiberglass E-cloth is available in the following styles
FYI the "E" in G-glass stands for "Electrical Grade" fiberglass as it was initially developed for electrical wire insulation but later was found to exhibit good reinforcement strength when coupled with a plastic resin.
S-glass (or S-2 glass) and was developed for military and ballistic applications. S-glass has a much higher tensile strength and modulus than E-glass and is approximately 10% stiffer and 30% stronger.
S-glass strands are produced at higher temperatures and require more expensive machinery therefore the cost is a bit more. S-glass is a bit "stiffer" than E-glass or WARP glass but laps around rails fairly easily. Laminating a surfboard with S-2 fiberglass cloth will greatly decrease heel dents and dings if glassed on the deck wrapping the rails.
S-2 Woven fiberglass cloth is available in the following styles: