I’ve started a hobby that I probably won’t finish (but I’ll try anyway). I’m building a canoe using “Building Your Kevlar Canoe” by James Moran. However I’m contemplating carbon fiber instead of kevlar. What I’ve been able to find so far on the internet doesn’t convince me that one is clearly superior to the other. It looks like Kevlar is a bit lighter but more “floppy” and would require extra support to stiffen the boat up (which might make the boat ultimately heavier). Carbon fiber, while slightly more dense, is more stiff. I belive carbon is also stronger (in the sense that it doesn’t tear as easily??) but cannot withstand abrasion as well as kevlar.
Is there something I’m missing? Should I build with carbon fiber instead of kevlar? Will the carbon fiber ultimately make the canoe lighter? Or is the new carbon fiber technology overrated and not greatly superior to kevlar?
By the way, my current thought is to have a inner layer of carbon for stiffness, and a thin light outer layer of kevlar to protect the carbon from abrasion (instead of two layers of kevlar or one of kevlar and one of S-glass as the book says). I’m also open to suggestions for different lay-up configurations
Indeed, carbon fibre is stiffer and makes a better structural material than Kevlar, which has outstanding shear resistance (that´s why it´s used in bulletproof vests)
A carbon fibre structure coated with a layer of Kevlar sounds like the best option.
P.S. Be careful while working with the carbon fibre, the fibres are conductive and soon will be flying all around in small wisps; so either work outside or in a room with all the electrical stuff properly covered.
I certainly don’t have any special skills…which might mean I screw this up. The book is pretty easy to follow so far. The best part about it is that I’ll make a mold first, then build the canoe off of the mold. I can then re-use the mold for a second, third or even fourth canoe.
If I get it done and you are anywhere near Madison, WI; I’ll be happy to let you help and even use the mold for your own boat…no sense in having to go through the trouble of making your own mold.
Anyway, Sigene, I researched you book on USENET, priced some Kevlar canoes, and some Kevlar, and just ordered the book from Amazon. I’m not normally impulsive like this, but (1) I love canoeing but have only rented, and (2) this idea is so incredibly awesome.
Go after James Moran for your sales commission on the book…
The difference in layman’s terms between carbon fiber and kevlar is this: if carbon fiber is bent far enough, it snaps off clean, more or less. Kevlar will stay “floppy” because the fibers are really still flexible, they are stiffened only because they are surrounded by plastic. So if you take a long piece of each impregnated with (cured) resin and bend it until it breaks, the carbon fiber will snap and break more or less into two separate pieces–while the kevlar will be two stiff halves connected by a “seam” of flexible fibers, where the resin cracked and broke, but the kevlar fibers are still hanging on. So the kevlar “stays together” when broken, while the carbon “comes apart”.
So if you are making something that may get flexed a lot (such as a canoe bottom, that you want to flex when it hits underwater objects) then stick with kevlar. The oars however do not need to flex at all–and in fact you can buy carbon-fiber oars, I have seen them in outdoor shops. Rather pricy, but amazingly light.
~