On my WD12 and my wife's CH16LT I took it just high enough to cover the stitch holes at the chine. Since these were kit boats, CLC's CNC machine had very kindly made a perfectly spaced set of holes which acted as superb guides for the fine line masking tape. This covered the entire bottom plus the portions of the chines which got the worst wear. Here's how the Duck turned out:

Thanks Laszlo,

That does seem like the best approach.  Minimum amount of coating for maximum protection.  I will have to pick my own guide points as my kit was not predrilled.  Easy to measure however on the MC.

The biggest problem now is I hate to take the boat out of service.

PAG

I had even more questions when I planned out my bottom paint. I did the carbon/epoxy coat and sanded the finish though 600 grit in a bow to stern direction, orientating my sanding scratch to leave a visually appealing surface and to aid in wetting of the hull to improve laminar flow for greater speed. But do I leave it bare epoxy and risk degradation from sun? Do I overcoat it and ruin the "scratch worthinesss" of the carbon?

I can't really say if it helped or not in performance, no way to evaluate it in a human powered machine. So for purely asthetic reasons, I ended up overcoating it in black and clear automotive urethane. The rest of the kayak was sprayed in clear coat. I believe it was a product called "diamond hard".

 It's 20 years old now and still looks like new. IF I can figure out how to attach a photo, I'll do it.

Ps: GREAT finish Laszlo! care to share the details?

From my days of building carbon fiber racing trimarans, we used carbon throughout for strength but in areas that had potential impact risk (e.g., keel area), we used Kevlar (think bullet proof vests) as it is much better in puncture and/or abrassion strength than carbon.

 Although I admit carbon (left unpainted) is much better looking so you have to weigh asthetics over function.

Thanks. There's no details to share, really. That finish is a triumph of photography -it's the bare epoxy after the weave was filled. I guess that if there's anything to share it's that lots of very thin coats is much better than a few thick ones.

I left the bottom unsanded.Sanded graphite/epoxy ends up dull grey, like pencil leads. Unsanded is a glossy black.

Have fun,

Laszlo

The above discussed carbon coating will be going on an existing boat so it will be necessary to sand thru the existing varnish first.  The topsides of the hull are in good shape so I do not want to revarnish them.  What I have done in the past for similar situations has been to mask the varnish and sand to the masking.  This always roughs up the edge of the masking so I must remove the tape and try to match the edge with new tape before applying the coating.  It works, but is not the best.  Are there any wizzards out there who have found a better method?  If so, will you share?

PAG