Hi Marcus, 

a coaming/opening that works for you is so important for enjoying a kayak. 

i have been building a long time and have a pretty strict rule for myself that i need to be able to put my butt in the boat and then pull my legs in...and that just requires a certain size opening....so i routinely deviate from whatever is the 'standard' design to acheive this objective.  

so if the shearwater sport does the trick from a sizing perspective, i don't see a big issue with the retro-fit.  you appear to have already sorted it out based on what you wrote.

as to removing the old coaming, the main thing is you want to protect the deck from getting cracked/damaged while getting the old one off.  heat guns work well for softening epoxy....but it might be a bit difficult to get enough heat into the stack of wood that makes up a clc coaming to soften it up without doing damage to your exisiting hull and its glasswork.

in this design, since the risers are proud of the hull, i think it will be eaier to go in with a bendy blade saw and carefully cut it off....and that is probably how i would start.  i would just take my time and be careful, but i think you could make easy work of it with a small bansai saw.

any left overs could be quickly sanded off with 80 grit paper and a sanding block.

other than cutting through the forward deck beam, which you identified, i don't see any other significant issues.   the deck beam that you don't cut away should probably be left there.  i think any attempt to remove the remainder wouldn't be worth it and it does not need to be rebuilt as part of your work in my view.  i won't get into the specifics of why other than to say if the deck continues to hold its shape, between the new coaming, the deck, and the remaining parts of the deck beam, i think you have more than enough structure so that the boat is strong/safe.

h

   Thanks a lot hspira, that sounds good! :-)

   I feel that the deck beam on the C-17L is primarily for forming the front deck. If you think it is still necessary to keep the clamps from spreading, weight, etc you could add a doubiler layer or two just infront of the new cockpit. 

I would use the saw as previously suggested..  I cut the thigh braces, "keyholes"  on my cockpits too. 

Hi Grumpy,

could you explain what you mean with the double layer?

Thanks!

Bye!

Marcus

    double layer?....... no a "doublier" .  Its basically a layer of thin wood epoxied to the underside of the skin/deck to make that piece of deck thicker at that point. Kind of like laminating up a "deck beam" in place.  Think of it as taking a 2 or 3" wide piece of thin flexible wood and epoxy it to the underside of the  deck foward of where you cut it. Then clamp it. Then glue another one. Soon you have a thickened deck, doubler. On the final layer seal it in fiberglass/epoxy.  

Remember to ease the edges for the glass, no voids, and take the wood and glass all the way to the clamps. 

Thanks Grumpy, now i understand! :-)