If its trying to pop up once you lay it up and wet it out lay some wax paper over it then weight/tape/whatever works to keep it in place. Wax paper is like poor man's peel ply. I'd like to hear how it goes as I'm thinking of replacing my coaming on my LT17.

Lay your carbon fiber cloth down, wet it out and then trim the overlapping ends where it butts together so you get a clean edge. (leave the end dry until you are at the seam and then carefully trim with shears) Then lay a strip of 4oz glass over it. That will soak up the extra epoxy and hold the carbon cloth down. Wait till it dries, coat the glass to fill the weave and give it a light sand with 80 grit.  The 3rd coat of epoxy smoothed on with a foam brush or cut short nap roller should be smooth as glass and ready to light sand & varnish.

Oh yeah, I forgot... I've tried covering with plastic, wax paper, etc. and it works. The only thing is that you tend to get ridges in the epoxy when you squeegie it out. Then you have to sand them down and I invariably hit the weave of the cloth. I have been working with carbon fiber/kevlar cloth so it is even worse than the plain carbon. Laying down a single layer of 4oz glass clothsolves all those problems and you can sand it down as far as you want and not worry about it. Another coat of epoxy will fix wherever you hit the cloth.

Guys, thanks!

Here are some pics... my only problem was getting the seams (yes, I had to put one on both sides) to line up nicely.  Not sure if it'll show up in these photos.

Everything layed down nicely, no poping up (which was my fear over those butterfly wings).

I'm heading back to drape the 4oz glass over the seams; will then cover the entire thing with glass tomorrow.

Very cool stuff!

Apparently you slightly misunderstood my earlier post, but it should be OK anyway. I laid 4oz glass cloth (bias cut tape basically, although it was a strip cut from a roll of cloth) down over the entire carbon fiber layup while it was wet. That way it soaked up the excess epoxy and held the whoe thing down flat to the coaming. If you lay your glass cloth top layer down after the carbon fiber sets up, you will get the same effect, just with more epoxy. 

No worries... It looks great in the photos! Carbon is not really as hard to work with as it 1st appears to be.  

Jay,

Actually I did understand your approach, but I didn't have any 4oz cloth cut and my epoxy table was a dissaster (sticky black fuzz everywhere).  So I put the strips of cloth over the seams - held them down perfectly, you just see a shift in the weave but no fibers sticking up.  Tonight I'll do the layer of glass... and the 4oz is pretty easy on the amount of glue.

I considered using 6oz glass to ensure I didn't sand though it, is 4oz really enough?  It's definitely easier to put on/wet out.

Thanks again for your help, and yes, it does look great!

Larry

If I added it up correctly you have 2 layers of 4oz, 4 layers of 6oz, a layer of carbon fiber and then more 4 or 6 oz glass cloth. A total of 8 or 9 layers. The carbon is stiffer than the fiberglass so I think you will be OK with that. I have not made a coaming with that type of layup but you can always add another layer of carbon and glass later if it flexes more than you feel good about. When it is attached to the deck, I'm guessing it will be pretty much rock solid.

Jay, yes... 2, 4, one carbon and then one more layer of 4oz.  I' figured I could put another layer of 4oz on if it feels too flexible when I pop it off, but from everything I've read I think I'll be ok.  I don't want it too thick or too heavy (but I also don't want it cracking - I'd hang myself!!!).

Do you have any tips for cutting the shape out when it's cured?  I'm thiking jig saw but there are lots of wierd angles to deal with.  I could use a hand-held coping saw but that might take forever and require lots of sanding (which I'd prefer to avoid as much as possible).

Thanks again, it looks so cool!

Larry

I am not trying to be a smart-ass or anything, but why all the trouble to put carbon fiber on your coaming? Or are you making a coming out of glass and carbon fiber? I am just curious, because I just finished my WD12 and I put a layer of glass on the top and inside of the coaming that came in the kit, and the finished coaming is rock solid. Why would someone need a stiffer coaming than that? Thanks for any info.

Lafisher,

I made my boat from plans and never had enough plywood to make a coaming (as called for in the manual).  I found pictures of a glass/carbon coaming on the "One Ocean Kayaks" website and thought it looked very cool.  Mine is a compilation of glass layers with one layer of carbon. 

I wasn't thrilled with the appearance of the ply coamings and would have painted it had I gone that route. 

Larry

   Larry,

   I'm building a Shearwater 14 & 17 hybrid & would like to do the composite carbon cockpit coaming as well as the hatch sills.  Did you build a wooden lip that sits on the deck (permantley) & then shape foam around it to act as a mold for the coaming?  I'd appreciate any ideas you might have.

   Thanks Gregg

Gregg,

No wooden mold.  I used two 5/8" rubber hoses taped around the coaming (side by side to give me the width necessary for the lip).  I covered the entire "mold" in clear packing tape, which held everything firm and ensured an easy release after curring.  (The 5/8" hose came from an old air compressor hose I wasn't using.)

I layed down 5 layers (two 4oz and 3 6oz) of glass over the mold, let it cure, then came back with very thick epoxy and using my fingers, smoothed it over any bumps or dips, trying to give it a uniform shape all the way around.  A little sanding after that cured gave me a much better/ smoother surface.  My cockpit is the keyhole shape so I also put a large fillet in the area between those "wings" and the hoses so the Carbon wouldn't have to adhere to such a sharp curve (sort of obvious in the pictures) when I wet it out.  The carbon's pretty stiff and can have a tendency to lift if bent to drastically.

Everything else went very smoothly.  Be sure to read Jayarboro's comments earlier in this post on cutting the carbon at any seams and covering them with 4oz glass... this serves an important purpose, it prevents all those carbon fibers from sticking up in the air while they cure and needing to be sanded before the final layer/s of glass go over the top.  Any sanding of that CF will ruin the look of the weave.  I put one 4" wide layer over each seam, waited 8 hours and covered the entire coaming with another layer of 4oz... I had no trouble sanding the final covering smooth at it's seams without disturbing the carbon underneath.  (The nature of the glass will make the seams somewhat necessary... but they're invisible in the final result.)

This evening I put a coat of epoxy on to fill the weave of the top fiberglass and it looks stunning!  I highly recommend it.

Let me know if you need an online source for carbon fiber... I bought 1 yard, 50 inches wide, and it was easily enough to do two coamings.  Total cost was like $40.00.

Larry

    The hose is a great idea.  How did you attach the finished piece to the deck?  I bet it looks great, any pictures of the finished product?  I could use a source for the carbon fiber.  Thanks for the help.

    Gregg

Gregg,

Haven't attached it to the deck yet, have to sand the deck's glass/epoxy down in prep for varnish first.  Will attach the coaming with a thick fillet of epoxy under the lip and a slathering of epoxy around the edge.  Pics will follow but it might take a while.

Here's the link to my source.  The 2x2 Twill has an attractive weave (especially after being cut on a 45 degree bias) and it's light/thin enough to accommodate the compound curves of a coaming.  The 4x4 weave might be too heavy.  Just be sure to put 5 or 6 layers of glass underneath it for reinforcement.  The glass will provide the strenth, the carbon gives you the stiffness/regidity.

http://www.uscomposites.com/carbonpage.html

5.7oz Twill "1st Quality" Carbon Fiber @ $41.00 per yard.

Keep me posted and let me know if I can help,

Larry

   Thanks for the info,  look forward to seeing the pictures.

   Gregg

Gregg,

Here's a couple pics.  This has an additional layer of epoxy over the 4oz glass to fill the weave.  Will probably do that one more time as there's still some pattern showing through in places.

I'm almost regretting that I didn't go with all fiberglass and just paint it as part of my paint scheme... I'm reading on the web about how to cut carbon fiber (after epoxied) and getting everything from "be sure to wear a dust mask" to "very few people have the funds or technology to adequately filter carbon dust!"  This guy said the safest way to cut it is under water, that anything else leaves too much danger of exposure to the dust... which, of course, will linger on tools, floors, clothes, etc. for a long time, making it a cronic health hazard.

I'll keep reading and post when I've decided what to do.  My initial thought is to cut it outside (with a hack-saw - the prefered non-power tool method), wearing an industrial chemical/partical respirator, and then dispose of my gloves, shirt, sweats, etc.  I have enough lung issues (20+ years of smoking) and don't need to complicate my life with "carbonosis!"

More to follow,

Larry

   Larry,

   Looks great.  I wasn't aware it was so bad to cut.  I would think cutting outside with water should control the dust.

    Gregg

I use a dremel with a diamond wheel and it zips through pretty quickly. Then again, I did my strip hull forming with a Makita grinder and an 80 grit pad in about 30 minutes, so I'm not adverse to power tools and the fact that a slip can ruin alot of work. Just don't slip.

A hack saw may give you trouble on the inside curves because the frame will prevent you from making the turn. You might try a razor saw if the teeth are not too fine to cut through the cloth. A jigsaw with a fine metal blade should work well too.

When you attach the coaming to the hull, you will probably want to run a layer of glass around inside of the coaming rim and over the inside of the hull seam to attach them. I usually pick my Wood Duck up by the coaming, and there is alot of stress on the rim. You can flip the boat over on sawhorses & put something like a cooler under the cockpit to sit on and stick your head and arms into the cockpit, then run the glass tape around the inside rim and wet it out. A wide fillet of epoxy mixed with graphite powder will match the color of the carbon and smooth the transition. You want it to be smooth with no sharp edges because this is where you will rest the weight of the boat on your hand or shoulder when you carry it to the water. 

Jay, thanks for those tips.

I bought a metal cutting wheel set and a diamond wheel for my Dremel, will start (and hopefully finish) with that.  I'll use one of my grinding stones to smooth the underside of the outside edge (if that makes sense) before sanding/wet sanding.  I also think I'm gonna lay another layer of 6oz over the top; there's lots of little bumps and valleys... not terribly noticeble until the light is right, but then it shows off a lot.

This last layer of 6oz will be the one I wrap into the cockpit to give it that smooth connection... and I'll do a significant fillet between the deck and coaming, which eventually get's painted (the stripe on the deck (covering the nails) will go up to the coaming on either side to cover the butt seam, then circle around the coaming just to make it stand out a little - sea green paint). 

High temp today is 45; not sure I want to play with the dremel, in front of a fan, outside, in those temps so this'll have to wait until next weekend, earliest.  Have plenty of sanding to do on the deck/hull in the meantime.

Thanks again, all these posts have made me more comfortable with cutting this down.

Larry

Well, after reading all the controversial opinions about the safety (or lack thereof) of cutting carbon fiber, I'm seriously considering scrapping that idea and doing a traditional wood or fiberglass coaming.  It isn't that I don't love the look of the CF but I'm not at all interested in finding out after the fact that I screwed the pooch (i.e., me) by inhaling fibers and causing lung issues (20+ years of smoking did plenty of damage, would rather not complicate things).

I appreciate all the reads and good advice; will let you know if I change my mind.

Larry

Larry,

go to the link below, scroll to the bottom of the page and you can download a Material Safety Data Sheet from Hexcel, a manufacturer of carbon fiber. There's a phone number on the MSDS so you can get the straight scoop from Hexcel.

http://www.robotcombat.com/store_carbon_fiber_faq.html

Let us know what you learn.

Mark

Mark, interesting read.  Seems that there's no toxicological issue with CF, the only problem lies with the small fibers released during cutting/sanding.  Of course, the end of their MSDS had a nice "disclaimer" paragraph, but I suppose that's standard.

I'm still contemplating..., hate for all that work to go to waste.

Keep ya posted, and thanks for the link/info,

Larry

I've been cutting the stuff for a while now with a dremel. I'll let you know if I craok in the near future from that before something else gets me. I fail to see how a particle respirator would not catch it if it worked for aesbestos that is known to cause other issues as well.

It's your call, but alot of people do it every day for a living and the way I see it, a one time shot is almost no risk.

Jay,

I think  you're on to something here.  After reading the Safety Data Sheet I'm prone to think that particle masks, gloves and a little common sense will go a long way.  Actually, I can't see how it's much different than fiber glass (which, when sanded, puts out gobbs of noxious dust/particles!).  I guess I decided that if I haven't killed myself with smoking, drinking, driving (occasionally) like a maniac and various shooting sports, I can probably cut one carbon coaming without dissastrous results.

Perhaps I'm being too O/C (obsessive/compulsive), which I am.  Next decent day I'll set up my fan, workbench, etc., outside and have a go at it.

Thanks (again),

Larry