I use the cockpit cut-out for a pattern and then cut the coamings slightly oversize with a saber saw. Mark and cut the underside because the saw cuts upward and sometimes rips the upper ply. After the coaming is installed I round over the inside edge with a router, then plane and sand the rim to final shape and size. -Wes

Dave,

...or, you could go adventureous and do what I did, make your coaming from Carbon Fiber!  Looks awesome and is extremely strong.  Here's a few pics:

My post (long) has some details as to what I encountered and how I built it up (6 layers of glass over a home-made mold; two more layers of glass over the carbon):

Good luck with whatever you decide on,

Larry

I very carefully cut the top with a jib saw.  Then I cut the lower layers a little proud on the inside (that is leave a little extra material) including the deck.  I then use a template router bit to clean it flush to the top layer.  http://www.leevalley.com/en/wood/page.aspx?p=30166&cat=1,46168,46171 Once I have done that I again use the router and do the round over.  Comes out brilliant.  I did not do the same for the outside since lip overhangs.  So I was careful on my cutting of the outside of the spacers, not so much on the inside.  I then followed Lazslo's advice and glued the layers of the caoming together, on the deck to get the curve, but with a layer of plastic between the deck and the coaming so that could be removed, sanded and epoxied under the lip before final attachment.  http://morocz.com/BoatBuilding/DuckBuild7.htm  I routered the coaming on the bench before attaching and doing the final routering of the deck.  I would suggest you try a practice with some scrap first.

And yes, like you I am a plans builder.  My SOF & WD coaming came out awesome, there is still a little wave deviation here and there... but I'm OK with that.  The more better you are at cutting the top lyer, the more better the whole thing will turn out.  I plan to use the same technique for my C18.

Many thanks to you all.  The links were a great help.

Larry,  I think I'll stick to BS1088, despite the good looks of carbon fibre.  Starting to get the urge to finish the job (110 hours so far).

Dave