Carbon /Kevlar Hybrid Cloth

[Doug Canada]

Greetings,

During my visit the other day to Noahs (a boat building store) I spoke to someone concerning using a "Carbon /Kevlar Hybrid Cloth" for the building of a canoe.

Does anyone have any material that you could send me concerning the use of this cloth?

Is there anything on-line that you might refer me to?

Could you use a single layer of this cloth to make a canoe?
i.e., no wood or a second layer of cloth

Any one have any experience with his cloth?

Thanks,
Doug

.

[Jagermeister]

Bell Canoe (http://www.bellcanoe.com/) makes carbon/kevlar canoes, under their "Black Gold" options. The purpose is strength without weight, which means it is used as the only structure for the resin, and therefore requires a mold. I don't think this is intended for wood canoes.

I sincerely doubt it is possible for a one-off to duplicate the results Bell gets from their process. This is only my two cents, but if you really want a Carbon/Kevlar canoe, you are probably better off buying it from Bell rather than trying to make one yourself. But, "your mileage may vary".

I think I saw the cloth (a composite weave) at my local Tap plastics store, but they don't appear to have it on line. You might call your local store.

[Ron Williamson]

Hi Doug
I have a carbon fiber,single layer NovaCraft canoe.
It has 6 or 7 half-ribs to stiffen the bottom,but nothing on the sides so they're a bit willowy,but it's very light and fast(pretty tough too BTW).
Novacraft is in London,IIRC,so you might want to go exploring.
IMHO you'd have too build it over a mould,which is quite as much work as just building the boat and you can't paddle the mould when it's done.
R

[Cuyahoga Chuck]

There is a book called "Building your Kevlar Canoe" that covers the whole process.
But here's a thumbnail of what it takes.
You must have a mold. Usually it's a male mold. If you want a perfect hull the mold must be perfect. The mold take 3 times as long to make as the hull.
Normally a non-racing canoe has only a single layer of Kevlar covered by numerous layers of fiberglass cloth. Kevlar is a VERY high strength fiber. You do not want it anywhere it can be abraided. Torn Kevler forms tufts that cannot be sanded off and it is extremely hard to cut.
'Glass or Kevlar or CF potted in epoxy resin creates a material without much stiffness. It takes numerous layers of additional cloth (mostly 'glass is used) to get a hull with any stiffness. On large canoe hulls a 4 or 5 layer bottom will still oil-can so internal ribs must be molded in.
Kevlar is noted for it's "tensile strength". In most other measures it is not much better than plain old 'glass. When Kevlar is laminated to the inside of an epoxy/'glass hull the Kevlar's strength makes the entire sandwich much more resistant to punctures.
Carbon fiber can be strong and stiff but, if it is not layed up according to certain engineering perameters it is not much better than 'glass.
From studying the book I mentioned above I would say that building any king of 'glass/Kevlar/CF boat hull at home is probably the most difficult and time consuming method to be found. And it would be difficult to accomplish without at least three experienced people share the labor.
Charlie

[George Roberts]

There are a lot of Carbon/Kevlar cloths available. For example:

5.5oz/sq yd 2 x 2 Carbon/Kevlar Twill Weave at $38/yard in yellow, blue, green, red, or orange.

I think the above cloth is really 6oz. You can get similar in 2 or 3oz.

I expect a single layer of 2oz would not last very long.

[Rick Tyler]

I haven't read the book mentioned above, but I doubt you'd get good results without vacuum-bagging the whole hull on the mold. The resin-to-fiber ratio would get high without bagging, and the fiberglass/kevlar bond wouldn't be that great. Kevlar tends to float in epoxy.

[Todd Bradshaw]

As I recall, "Building your Kevlar Canoe" documents a rather backward method compared to production building. It can be used for a one-of-a-kind hull, but with certain limitations. They essentially build a plug from plywood stations and some form of station-to-station filler (strip stringers? screenwire? chicken wire? I don't remember). Then they slather the thing with drywall mud, fair it out and seal it. The Kevlar canoe is then built over this male mold. The outside surface of the cloth is filled and faired as would be done on a stripper. The process essentially "fills" the inside weave as well, leaving a smooth inside, but doing it by adding unneeded, extra resin and weight. People have been building test versions of production boats directly from the plugs this way for decades in order to test a design before investing in making a proper fiberglass mold (which is expensive and time consuming). But the layup technique is pretty limited. Most of the modern, high tech composite canoes use a fair amount of core material to generate stiffness with minimal weight (separate two load-bearing skins by a light, non-compressable core and you generate far more stiffness than those two skins would produce simply laminated together). This is normally done with foam on canoes and kayaks and may be as thick as 3/8" or so, stuck into the laminate between the layers. When you lay up a boat in a normal, female mold (working from the outside-inward) you can do this and the boat works just fine with visible raised ribs or a big bilge cookie on the inside of the bottom. The outside of the hull is still smooth.

When building "backwards" over a plug or male mold (from the inside-out) as documented in the book, you generally have to achieve almost all of your thickness and hull stiffness with little more than multiple layers of fabric. Any coring that didn't evenly cover the entire hull would leave big raised lumps on the hull's outside which would need to be filled around unless you can figure out a way to recess them into the mold to generate a smooth hull. You could lay up a partial hull (mostly a heavy skin) remove it from the mold and then go back in and laminate foam ribs inside of it, but you would be getting into an awful lot of work and it's fairly risky. The heat from the inner layers curing would probably be enough to deform your previously fair hull skin.

Without substantial coring there may be a few places on the hull that would have adequate stiffness and strength with only one layer of the right fabric, but they generally won't be the parts that keep the water out. All in all, when you consider the cost, labor and highly experimental nature of the process, you're better off building a stripper or buying a production Kev/carbon boat that you can actually get some use out of.

[Gerald]

I recently built a strip dingy. It is a deep and only eight feet long. The shape was exactly what I wanted but the strips didn't want to cooperate. I was not happy with the finished product so I used it as a plug. The seat boxes are the stiffeners. I added enough foam to the boxes for extra stiffness and to make sure that the dingy cannot sink.
For a one off boat the internal plug method worked out very well for me. I have a 24 inch air file that made fast work of fairing the outside. Obviously the file will not fit the internal contour. I used fiberglass cloth instead of carbon or kevlar since weight was not a major concern. The wooden, varnished stern and seat tops make the boat look like a strip built that has been painted.
I have never worked with kevlar. However, someone recently told me that they could not cut kevlar with metal shears until they added a piece of tape to the cloth and cut thru the tape and the cloth at the same time. He claimed that the tape held the fibers in alignment? Is that true?
Gerald

[George Roberts]

Gerald ---

That is my method of cutting kevlar.

[jlapratt]

The most recent Professional Boat Builder features two builders of kevlar/carbon fiber canoes. Both use female molds with no vacuum bagging.

Jeff

[cedar savage]

My first attempt at a composite canoe was a kevlar/fiberglass/carbon fiber sandwich.

I used a finished cedar strip Wee Lassie. Shrink wrapped it. Fitted a layer of rip stop nylon over the shrink wrap. Layed up the cloth with the carbon on the inside, the fiber glass in the middle, and the kevlar on the outside. Used a squeegee to force the epoxy into the three layers. Then I used one of those epoxy rollers with dime sized metal circles to force the layers together. The inside is non-slip textured from the peel ply layer of rip stop nylon. The outside had only one additional weave fill coat of epoxy.

The finished product is uglier than sin on the outside. Something about the materials used causes the canoe to look puke green. There are also wrinkles from problems with the fit of the rip stop nylon underneath.

The nearly 12 foot canoe has 2" glass tape under 1.5" x 0.25" mahogany in/out wales, a mahogany stiffener running the length of the bottom with two layers of fiberglass tape over, and two maple thwarts and two handles.

It weighs 18 pounds and is a dream to paddle.

The next one will be made from two layers of kevlar.