: I have an idea to file a groove in my hatches and then use an o-ring to keep
: them watertight. Both front and back hatches are egg-shaped and will be
: mounted flush to the deck.
: Any comments?
: Thanks Jim

Maybe cut the groove with a router and a half round bit so the O-ring would fit nicely in the groove. The router could have a guide on it so the groove would be the same distance from the edge of the cover all the way around. Once the groove is cut, coat it with a layer of epoxy to keep the water out of the wood.

Just make sure you don't screw up, you only have one hatch cover (for each hatch) that matches the rest of the kayak. Good luck trying to make a new one that matches. Maybe you should practice the technique on scrap first.

The nice thing about the groove being in the lip instead of the cover is that the water has to go up over the foam. If there is an O-ring in the cover, the water just has to find a way under the O-ring to get into the kayak. In other words the O-ring might not seal as well if it isn't a tight seal all the way around.