: Hello all,

: I know “plastic” is a bad word in this forum,
: but hey ! he got epoxy and FG and more stuff.

Epoxy and even varnish are actually plastics once they cure. They're just not commonly referred to as such in boat building circles.

: well, I visited this place: : www.plasticworld.ca

: I saw there (among other things) 3 types of materials, I talked
: with the person, and following is the information I got from him:

: FG – irrelevant for this discussion

Not really. There is more than one type of fiberglass suitable for use in kayaks and it it has some advantages

: Kevlar – light brown color cloth with the same complexion as FG .
: He claims it is heavy

It's not necessarily heavy, but it can result in a heavy layup, depending upon how it's used.

: and expensive, and more abrasion resistant,

True.

: Carbon fiber – black cloth with the same complexion as FG .
: He claims it is light and expensive and stronger than the FG.

True.

: He also said something about one material being more abrasion
: resistant than the other, and about the “other” that will no break when
: folded, unlike the “one”, but I don’t remember which is which.

Kevlar is much more abrasion resistant than carbon fiber and it does not fracture.

: To this very day I had the belief “Kevlar” is just a brand name
: for carbon fiber.

No, they are completely different materials with very different properties.

: The person there seemed impatient so I did not
: started this discussion with him, and the truth is I trust the
: people here more than I trust people that are not…. well….. “here” .

: so:

: 1.
: What is that light brown material called “Kevlar” ?

It's a para-aramid fiber made by DuPont.

: 2.
: What is the difference between that “Kevlar” and the black “Carbon fiber” cloth ?

Carbon fiber is as its name implies, fibers of carbon. That's why it's black.

: 3.
: What are the pros and cons for our cause (which is kayak building)?

Carbon Fiber
Pro: Strong, stiff, light
Con: Expensive; low abrasion resistance; can be difficult to shape into compound curves due to its stiffness; finding it can be difficult, as demand from other industries is very high right now
Best uses: Internal reinforcing/stiffening layers where it is protected on both sides by other materials. It also works well in applications where it won't see much abrasion, such as the underside of a kayak deck. It is also commonly used for coamings, where its stiffness and appearance are advantages.

Kevlar
Pro: Strong, flexible, very abrasion resistant
Con: Expensive; will become fuzzy when abraded; absorbs a lot of resin, especially when used in hand layups
Best uses: Inside hulls or as an inner layer in a laminate where it will serve as a puncture and fracture resistant layer. It is also often used for skid plates on canoe hulls. For best results it should used with vacuum bagging or resin infusion in order to minimize the amount of resin the fabric is allowed to absorb.

Before you get into working with these fibers, there are other materials you need to consider:

Fiberglass (E-Glass)
Pro: Inexpensive; reasonably strong; abrasion resistant; wets out clear
Con: Heavier than some other materials and not as strong
Best uses: Good, general purpose reinforcement for all boat building applications; decks and hulls where the wood must show through

Fiberglass (S-glass)
Pro: very strong; very abrasion resistant; less expensive than carbon fiber and Kevlar
Con: More expensive than E-glass; may not wet out clear
Best uses: S-glass probably has the best combination of strength, price and weight of the materials under discussion, but it isn't commonly used due to wet out issues and cost; it's best used for inner layers on hulls and decks and outer layers that will be painted; some types will wet out well enough to be used on clear decks and hulls

Dynel (polyester)
Pro: Light; flexible; VERY abrasion resistant
Con: Will not wet out clear: absorbs a lot of resin in hand layups; some form of compression should be used to prevent excess resin absorption
Best uses: Keel strips and other abrasion protection layers, especially if they are tinted to hide the fabric

As you probably have gathered, there is no single material that's perfect for all applications in kayak building. To some degree, they are all a compromise between performance, aesthetics and cost. You have to decide what is most important to you and choose your material(s) accordingly.