My observation is that these questions always require a picture of the damage to get a worthy answer. 

Steve, 

sorry to hear about the crack.  ouch. 

i think i would simply say it happens some times.  i have built a number of the CLC designs that have a 'tortured' deck -- the one that you bend around a curved form or bulkhead and nail into a sheer clamp.  and yes, i have broken one pretty much as you described.  it was actually on the first kayak i ever built from CLC.

since then, i have successfully completed a number of boats with tortured decks and not had the same fate.  the key thing i learned was about using lots of straps or tape (and often a second pair of hands) to evenly distribute the bending pressure and when i was actually doing the nailing, ensuring that i had already bent the wood to be in contact with the sheer clamp so that i was not trying to bang a nail into a piece of wood that was not properly backed.   i also was careful to not to bend the wood from its edge but to pressure it down where it would come into contact with the sheer clamp.  if you try to press the wood from the edge, i think it is more likely to break.  (the wood sometimes has a pretty substantial overhang that will get cut away after you attach the deck....so when i am pressing the wood down i always make sure i am not bending it from the overhang...but inboard from that).

anyway, i figure it happened on my first boat becuase i was just learning and really didn't know how hard i could bend or bang it before it would snap.

so again....sorry for what happened.

as to fixing what you have....  in my case, i was able to stabilize the cracked area and complete the deck attachment and then used wood flour thickened epoxy carefully applied to fill the crack and faired it in nicely and just completed the deck as normal.  i also made sure i put unthickened epoxy on the back side of the crack (by reaching under the deck) after i had dealt with the outside, to ensure i did not have exposed wood that water could get into.   

the crack remained visible for the life of the boat (it was a brite deck as well) but was not overly obvious (i pulled the paint line up onto the deck a bit) and seemed  at the time, a better solution than getting a replacement deck and starting over.

the only other solution i did consider was a new deck piece...and like i said, i ended up not doing that and living with it.  i am not sure there is much of a good solution other than that (e.g., a partial patch).   but i suppose that's an option.  in addiiton, like i mentioned, i tweaked the paint scheme a bit and hid most of it.   depending on where the crack is, that is certainly an option worth exploring.    not sure if there is an easy answer here.....as grumpy mentioned, if you attach some pictures, we can come up with some ideas.

h

   Perhaps you can keep the deck mostly bright, but use a decorative paint pattern or swirl to turn the flaw into a feature. Let the artistic you run wild!

   Had a difficult time myself on the same build. Seemed at one point I was not going to be able to bend enough to get it on. I know hindsight is 20 20 but saturating the peice with water helped and all  worked out fine. A bit scary though. 

? Did you epoxy the underside and allow it to cure? If so the piece becomes to stiff to bend and may have been the issue. Just guessing 

Sorry I have no answer for the repair since never having experienced this myself.

If it's any consolation I do recall being told that anything that goes wrong can be corrected somehow, some way. Hang in there. I'm realizing this is a thinking mans game, not as easy as just connecting the dots. PP