(a) Sketch a water-tight door and frame showing manner of attachment to bulkhead and the additional reinforcement carried by the bulkhead to compensate for the aperture. (8)

(b) Explain how water-tightness of the door and frame mating surface is ensured with an hydrostatic pressure tending to force the faces apart. (4)

(c) Describe the means of remote closing operation of the door and state how many closing stations there are and their position. (4)