Confused about what means what when it comes to surfboard glass? Let Rusty explain. Photo: Rusty Surfboards
Editor’s Note: This feature was made possible by our friends at Rusty Surfboards.
There are two standard weights of glass used in surfboard construction. Commonly referred to as four ounce and six ounce, they are actually 3.7oz per square yard and 5.6oz per square yard, respectively.
There are two common types of woven fiberglass cloth used in surfboard construction, E-glass and S-glass (or S-2 glass). Fiberglass fabrics also have a finish on them, which is there to help the resin bond to the glass fabric and to help it wet out completely. Early fiberglass and foam surfboards were built with existing fiberglass boat fabrics, which were finished with a Volan finish. The Volan finish produces a “coke bottle” green tint. Modern surfboard fabrics use a silane finish which goes absolutely clear. The silane finish is compatible with both polyester and epoxy resins.
Four oz. E fiberglass cloth is the most commonly used fiberglass cloth when glassing a surfboard. E-glass is easy to wet out with polyester or epoxy resin and laps around the rails easily. If you want the lightest weight surfboard, the common layup is two layers four ounce E-cloth on the deck and one layer of four ounce E-glass on the bottom. Surfboards made with all four ounce fiberglass cloth are light but not the strongest…unless you use S-2 glass, which I’ll get into later.
Fiberglass E-cloth is available in the following styles
4 oz E-cloth x 30″ wide
6 oz E-cloth x 30″ wide
4 oz E-cloth x 42″ wide
6 oz E-cloth x 42″ wide
FYI, the “E” in E-glass stands for “Electrical Grade” fiberglass. 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) was developed for military and ballistic applications. S-glass has a much higher tensile strength and modulus than E-glass and is approximately 10 percent stiffer and 30 percent 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.
Warp glass has more fiberglass strands, or heavier, running lengthwise. The four ounce fabrics are equally as easy to use, but the six ounce Warp is somewhat more difficult to get the bubbles out of than the plain weave fabric.
Warp glass also holds color laminations very well due to the increased amount of glass managing the pigment or tint spread. Some laminators will gently tug on the outer edge of the cloth during prep to take it out of horizontal alignment, which helps prevent shearing.
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:
4 oz S-2 fiberglass cloth x 30″ wide
6 oz S-2 fiberglass cloth x 30″ wide
There are quite a few other weights of cloth. Two ounce, five ounce, 7.5 ounce, 10 ounce, and more. Types of cloth include Innegra, Bi-axial Innegra, Aerialite, Vector Net, Biaxial, Triaxial, and Carbon, Kevlar, Carbon/Kevlar blend. Carbon tapes, Kevlar tapes, and on and on.
My thoughts are 4E and 4S makes a strong light deck. Combo. You don’t want all S-cloth, as it can stiffen the board up. While it will be more dent resistant, it will have a higher possibility of shearing or buckling. For the same reason, you don’t want it on the bottom as well.
Five ounce with a 4S deck is a little stronger. Combined with a five bottom, it makes for a light yet reasonably strong board. The combinations are endless.
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