I am finally going to build a butterfly hatch for my sailboat. I know how to build the hatch itself. My problem is trying to figure out how to stop the leaks from the piano hinge. I'm thinking of running an extra piece of wood under the joint where the hatch closes and make a channel to run the water out of the ends of the hatch. Does anyone know of any other way?. Butterfly hatches are known to leak at the hinge area, but they are sooooo cool looking as well as functional.

Thanks in advance