http://www.clcboats.com/forum/clcforum/thread/5940.html

CZ,

The link above will take you to my historical build post, with LOTs of pictures.  I used carbon fiber to make my coaming, a light, low-profile and very attractive coaming (now that it's shaped, sanded, and re-coated with glass and epoxy).  You'll find pics towards the end of my postings.

All that said, carbon fiber is a "bitch" (please excuse the french) to work with, mostly because of its health hazards.  Cutting the dry cloth, cutting the molded carbon, and/or sanding the edges exposes you to fiber dust that you don't want to breath.  I covered my body completely, did my cutting (Dremel diamond cutting wheel) and limited sanding outside to keep from having particles in my shop.  I have yet to wet sand it for varnish, but as it has a layer of 4oz glass and two coats of epoxy over top of it, I'm not too concerned about that.  If you can keep your lungs covered while you're working with it, it does produce a very stunning end result.  If you're planning on using it, do some Google searches on the material and read up on the safety precautions. 

One last point, if you find yourself having to seam it (as I did on both sides of my cockpit), saturate it with epoxy first, then carefully cut it with shears (kitchen shears work well) along the weave line while it's wet.  Cutting it dry leaves a fuzzy edge that's noticeable afterwords.  Also, have a 3-4" piece of 4oz glass handy to lay over the cut line once you align the two pieces; this helps hold the carbon in place and holds the seam down tight..., a better finish.

If you decide to use it, post your results.  I love the coaming on my boat, but because of the hassles of using it I won't be putting it anywhere else.

Sorry for the long post, but it's all good stuff.

Enjoy my pics, and good luck,

Larry

super strong, ultra-light material.  The reason its not used exclusively in large-scale yacht operations is its prohibitive cost.  

~Chris 

Carbon fiber is very stiff for its weight. It's about 9 times stiffer than fiberglass. So it only takes 1 layer of CF to make something as stiff as 9 layers of glass, which means that you only need 1/9th the epoxy if you use CF. Layer for layer, it's also a lot lighter than glass. The fact that it's lighter and that you need less of it results in some shockingly light structures. My commercially made CF paddles weigh 26 ounces. My homemade 10-ft CF mast wieghs 2 lbs without its fittings.

CF is brittle, though. It bends a little, but if you exceed its strength it shatters.

There are 3 main forms used in boatbuilding. There's uni-axial, where the threads mostly go in 1 direction. It's used to give stiffness in one specific direction, such as along the length of a mast. Biaxial is used where strength is needed in 2 or more directions. Woven is similar to glass and is used where a smooth surface is as important as ultimate strength. Woven is weaker than biax because the fibers fold over each other, but it lays smoother than biax.

Uni and biax are also available as tubing. In that form they are very convenient for making masts and paddles. There's no seam or overlap and each part of the cross-section is equally strong.

It is expensive compared to glass, but if you look at it as a complete system (fewer layers, less epoxy) and consider total cost per unit of stiffness per unit of weight, it's actually competitve with or better than glass.

Laszlo

Wow thank-you for your replys and the wealth of information.

Chris good to hear from you again.

Larry nice post ---your epic journey is well documented and informative--Oh and the CF coaming looks great ---so how many layers of glass and CF are we talking about ? I can not imagine that their could be any flex after that process. Good points given for health pre-cautions when using carbon fiber.

Laszlo--I can always count on your explainations to be informative and if technical will be explained so that us common folk can grasp what you are talking about-well most of the time anyway. Interesting about the different "weaves" of CF and the properties of each.

If memory serves me correctly in Nicks blog he was applying CF to the underside of a stripped top of a kayak. given it's weight and strength properties  this makes sense....CZ

Cz,

I laid up two layers of 6oz glass over my mold (which was simply a double (side-by-side) 5/8" air hose taped around the cockpit); followed that with two more layers of glass (6oz); applied thickened epoxy to even out the uneven spots - particularly in between the two hoses - so I'd have a good bed for the carbon.  Then I glopped on unthickened epoxy over the entire surface, laid one layer of carbon fiber, and then thoroughly saturated it with epoxy resin, soaked it through and formed it over the mold.  I followed that with a double layer of 4oz glass, but this was to give me a good top-coat that I could sand/smooth out without cutting into the carbon cloth itself (don't want to sand into that 'cause it ruins the weave).  Atop that I put a couple coats of unthickened epoxy to fill the weave, then sanded that to a rough finish, and recoated with one more coat of unthickened epoxy.  Smooth as a baby's butt!!!  I'll wet sand the final surface and put about three layers of varnish on it for UV protection.  All told, about 6 layers of glass, one layer of carbon (and the stuff is so amazing it still almost seems translucent!).  I also slathered some thickened epoxy on the underside of the curve to beef up the form for strength... may have been overkill but I've very little experience here.  Once I epoxied it to the boat, it was VERY stiff, still very light-weight, and (as someone told me) you probably can't break it with a hammer!

Good luck - great stuff if you can avoid breathing in the dust/fibers.

Larry