Paul,

The word "strength" presents a problem to our conversations because there are several different kinds. For example there is tensile strength, modulus (i.e. stiffness), modulus of resilience, hardness, and shear strength. The three fabrics in my sample very widely among these strength variables. CF is highly superior in modulus, but inferior to s-glass in tensile strength and highly inferior in resilience. As stated in the 11/2002 issue of Sail Magazine, the sum of these properties determines what each laminate is best suited for. Not being an engineer, let alone a laminates engineer, I have to struggle to figure out what will give me the lightest and strongest boat. Often I rely on industry practice as long as I know why certain things are used, but I also pay attention to certain innovative individuals. The problem with industry practice is it often is trying to minimize cost, while that is not necessarily my focus.

Unfortunately my blathering on about the different strength types does not help kayak builders very much. So let me stick my neck out. With regard to kayak building, I have concluded that CF is great for small things like fittings, hatch lips, and localized stiffeners. Since common glass schedules seem to yield a hull of adequate stiffness, I don't see any weight or overall strength advantage in using the commonly available 6 oz. CF for hull lay-ups. Since CF is so much less resilient, I would be worried that a nasty collision with a rock would result is much worse damage than if the hull were laminated with s-glass. Read the article in Sail Magazine (11/2002). It was an eye opener for me.

Ted

: Ted,

: I always thought carbon fiber got its reputation for being stronger than
: fiberglass for a given weight. I.e. pound for pound CF would be stronger
: (all things being equal) than FG. The thought being that you can make
: something of the same strength with CF, as the FG equivalent, however, the
: CF item will be lighter. Does that make sense?

: Paul