kevlar canoe

[blair50]

I am contemplating building my first kevlar canoe. I will have a bunch of free time on my hands and so I am eager to start a project that will keep the engineer in me happy. I picked up of a copy of Moran's book, Building Your Kevlar Canoe, A Foolproof Method and Three Foolproof Designs. The text is more than ten years old so I imagine that there has been changes since then. He recommends that the kevlar used should be no less than 8.9 ounce thickness. Most all of the places that I have found that sell kevlar sell stuff that isn't nearly that thick. I was wondering if anyone out there has built a kevlar canoe and can give me some advise. Any help would be appreciated.
Thanks

[Tim B]

Why Kevlar? why not Carbon and Glass (or Carbon-Kevlar)? what are you planning to use it for????

It's often quite hard to justify the use of Kevlar, unless it is for impact strength (usually at failure).

Tim B.

[Wellydeckhand]

Where can u get kelvar?..................? thats the quwestion

[blair50]

Kevlar is extremely tough and very lightweight. I can't think of any other material that is lighter without compromising the strength of the canoe.

[Wellydeckhand]

I know.......... balastically enduring........... do u have a supplier?

[blair50]

I have been browsing the internet for a supplier, and have seen a couple of promising sites. It isn't real easy to find and I worry about overpaying since there isn't a huge market for the stuff.

[Wellydeckhand]

Can u post the URL? Thanks before hand for the help.

[marshmat]

I've only ever worked with Kevlar as a prepreg, so this advice may not hold in your case.
If you need a total laminate weight of 10 oz, I much prefer doing this in two 5 oz layers than one 10 oz. The lighter cloth is easier to drape and 2 layers of thin cloth is somewhat harder to damage than one of thick cloth, as well as making it easier to reinforce high-stress points. The extra time spent on layup is well worth it. It is ABSOLUTELY ESSENTIAL that your mold be good! If the mold is slightly wavy or irregular, or has a bit of a texture, the boat will come out far worse. About 80% of the time spent in one-off composite construction is in the building and preparation of the tooling. The Kevlar will be expensive, yes, but you don't need a huge amount of it. Use a good epoxy resin and mix it well; polyester on Kevlar is just a waste of good cloth.

[blair50]

Thanks marshmat for the advise.

here is a couple of URLs.
http://www.raka.com/Kevlar.html
http://www.fibermaterialsinc.com/kevlar.htm

[blair50]

When laying down two layers of kevlar, does one put a layer of s-glass between them or just on top?

[marshmat]

You can put S-glass, kevlar, E-glass, carbon, whatever, in whatever order you want. Some combinations may work better than others. The layup is dictated by the intended load conditions and designer's whim, not by any set formula.

[Russ]

Hi,
One thing you should remember about Kevlar. NEVER put it at a surface you have to sand on. If your mold is perfect, fine, you can choose to use a clear or colored gel coat or if you are using a vacuum system you can get away without the gel. However if sanding is needed always put a layer of glass next to the surface. Sanding Kevlar or Twaron (the european version) will turn into a fuzzy mess if you sand it.
PS, Try a site for Kevlar named "theengineerguy" he is a distributor of exotic Composite materials and he was my indentured servant for the early part of his life. (SMILE), his dad!