An often raised question is the construction of cockpit rims. On some designs it is hard to get the spraydeck in place and hard to avoid leakage at the hem.
Often I notice that rims on wooden kayaks are s-shaped seen from the side. Such a shape is sometimes the result when building kayaks with flat decks and large height difference between fore and aft deck - like Black Pearl. The consequence is that the spraydeck slides off at the sides when trying to get the front part in place, and one should need three hands. When finally in place it may leak because the pressure is uneven round the perimeter.
With an S-shaped rim you might need a little more width on the flange. But then you will need a very elastic spraydeck to go over the rim and then create pressure on the rim. Neoprene normally does this very well, but Chillcheater´s AquaTherm is not that elastic.
With a flatter rim those problems disappear. It is easy to attach the spraydeck and it will seal against the rim. The flange does not need to be wide – 15 mm is enough – which means a slightly smaller hem and better pressure against the rim.
The simplest way to control the shape (without doubling the number of molds) is to use a temporary cockpit dummy (particle board or plywood) attached to the station molds when stripping the deck. Then it is just to force the the strips to land at the edges of the mold instead of finding their own curve depending on flexibility.