You can add a child of constraint to your cloth sail and add the rigid body to the influence object. That way, the cloth will move with the rigid body. If you want the rigid body to be affected by the cloth, so then you're probably using a force to make the cloth move: so definitely the rigid body will be affected by that force, so it will visually look like the sail is affecting the movement.
Edit: You've done two things wrong. First thing, make the sail the child of the stick, not the stick the child of the sail. Second thing you have to do is to hook the vertex of your object to an empty like this: Pin cloth to model