The fiberglass resin layer of surfboards offers strength and durability to the board. Different surfboard designs may use different weights of fiberglass and different types of resins. Before deciding on how you want to glass your board, take a closer look at the options available to you.

The Fiberglass Cloth
For the fiberglass resin process, you’ll start out with fiberglass cloth. Foam blanks are too porous and weak to be used in the water on their own, so the fiberglass resin layers must be applied to the entire width and length of the board, both on the bottom and on the deck, providing protection and strength.

The two common weights of fiberglass used for surfboards include 4oz cloth and 6oz cloth. Of course, while fiberglass continues to be the most popular choice for strengthening a surfboard, other materials may be used by some shapers. Both carbon fiber and Kevlar have been used to provide strength and durability to boards, and even hemp cloth, an all-natural material, has been used instead of fiberglass cloth.

Resin Choices
The fiberglass cloth is applied directly to the board, but when glassing a board, the resin must be used to help bond the fiberglass cloth to the foam board. Once the fiberglass cloth is in place, the resin is poured over the cloth, saturating the cloth completely. As it dries, it bonds the cloth to the foam board, hardening to create a durable, hard layer.

Since the 1950s, polyester resin has been used on surfboards. However, within the past decade, epoxy resin has become a popular choice. Epoxy resin continues to surge in popularity because it offers better strength while making it possible to keep boards lighter. While polyester and epoxy resin both can be used with polyurethane foam, if you use polystyrene foam, you can only use epoxy resin on it. Polyester resin cannot be used on polystyrene foam, since it will immediately destroy the structure of the foam when applied.

Of course, when you are ready to create the fiberglass resin layer by adding the resin to the fiberglass cloth, you’ll need to mix together the resin with a slow or fast catalyst. Once you create the mixture, it is spread over the board evenly, allowing the layer to dry. A hot resin coating will also need to be applied quickly. Once the hot resin coating is applied, it’s important to avoid pushing it around too long, since it could cure with bumps or brush strokes, making it tougher to sand the board later.

After adding the fiberglass resin layer and topping with the hot resin coating, you’ll need to sand the entire board after it has cured. Sanding the board at this stage helps to give the board a smooth, beautiful finish. The sanding process allows you to eliminate any uneven areas, but carefully applying the resin and hot resin coating will reduce the amount of time you’ll need to spend sanding the board.