You may want to read this C&P from the fcd surfboards site. FCD, while being a company unto itself and run by Fletcher Chouinard (his Dad, Yvon, owns Patagonia, Inc.) is very much a part of the Patagonia umbrella.

"The Foam
Since 1999 we’ve used extruded polystyrene, which is similar to the foam used in beverage and fast-food containers (Styrofoam®). This foam contains no VOCs (volatile organic compounds), a source of air pollution. Extruded means the material is forced through a small opening, like toothpaste is extruded from a tube. This gives the foam directional properties similar to wood or a honeycomb. As such, the foam has a constant density throughout.

The most common complaint about epoxy boards in the past is that they didn’t flex. However, we’ve found that they can be engineered to flex as much or as little as you want them to, depending on how you glass them. Our stock boards tend to provide a happy medium of weight-to-durability, so the average surfer will be able to keep his favorite board for a long time. A lighter weight board might flex more, but will be less durable. For those surfers who can really tell the difference, we make more flexible boards that are still tougher than the industry standard.

The higher compression strength of extruded foam means a stronger core to resist the downward force of the outer shell under a load. Lighter than average foam allows us to put more layers of fiberglass in the outer shell. This increases strength and resistance to breaking and buckling. We’ve built a state-of-the-art glassing facility, and worked carefully with materials manufacturers, to ensure the best craftsmanship and perfect resin-to-glass ratio for max strength and minimal waste. The entire process is done in Ventura, CA, and complies with the strict environmental laws of the USA.

Stringers
The stringer is the backbone of a board; a board without a stringer is like a body without a spine. You can add stiffness by making the skin or shell stronger (as is done with sailboards) but then you lose flex and the board feels dead. Too much flex, especially on a longboard, and the board feels slow and mushy. A board with the proper ability to flex should have a certain timbre that feels alive. All the components of a surfboard have to work together for proper rigidity, flex and strength.

Stringers contribute to a board’s strength by creating an I-beam within the foam/cloth/resin composite. In our stock boards, we use renewable woods with a high strength-to-weight ratio. This allows us to use laminated stringers that are stronger than single-ply, especially in the critical areas of the nose rocker. Because each size and style of surfboard has different strength and flex requirements, we use different stringer arrangements. A laminated stringer 1/8” to 3/8” wide is standard; the specifics vary depending on the board.

Fiberglass
A surfboard will buckle or break first on the side that’s hit (compression side). The industry-standard shortboard – with two layers of 4-oz. E cloth on the deck and one layer on the bottom – is only as strong as its weakest side. It will easily snap if hit by the lip. For reliable strength, a board needs more than one layer of glass on the bottom.

Both the type and weight of fiberglass cloth used affect a board’s strength. Warp glass has heavier fibers woven in one direction of the cloth. When oriented along the length of the board, it adds stiffness and strength, eliminating the need for a heavier, balanced-weave cloth. Two layers of 4-oz. warp is the minimum amount of fiberglass you’ll find on any one side of our boards.

Epoxy Resin
In the ‘70s and ‘80s, epoxy boards gained a bad reputation because often the wrong formulation of resin was used, and there was an unbalanced marriage of the various components. Most of these epoxy boards were also built without stringers. Resin technology has progressed since then, and the epoxies today are far superior.

There are thousands of different formulations of epoxy resin, depending on the intended use. The resin we use is blended to balance tensile strength, flex, hardness, impact strength and nontoxicity. It is about 2.5 times stronger than polyester resin and 300% tougher. This is important for ding resistance and durability over time.

Some epoxy laminators use polyester resin for the hot coat to save labor and material costs. But the two dissimilar materials often bond poorly, meaning the polyester hot coat will eventually chip off of the epoxy-laminated glass underneath. To prevent this, our boards are 100% epoxy for maximum strength and durability.

We use a UV inhibitor in our epoxy, which can give the board a slight purple tint when viewed indoors in certain lighting conditions. But outdoors the board remains an eye-blinding white. This is not to say they will never yellow, as any board left in the sun over time will see the effects of UV exposure."

There are cheaper ways to make a surfboard style composite structure, but this one is the strongest and has the most potential to last under tough conditions.

Should be a fun project.

Chris Ostlind
www.lunadadesign.com