Ulster folk & transport museum. A living history experience in the outdoor Folk Museum, Holywood, Co Down. Titanic Exibition.  Take a peek at one of Titanic’s actual portholes recovered from the bottom of the Atlantic. By looking at the way the sides of the frame are clipped vertically to fit properly, we know that this is likely a porthole from the Third Class section of the ship. The size and construction of the 9 different kinds of portholes on Titanic were strictly regulated by the Board of Trade to make sure everyone on board had plenty of light and air on their journey. Artefact on loan from RMS Titanic. Looking at this fascinating plan you will discover why the damage to Titanic’s hull led to the ship sinking. Bulkheads are steel walls in a ship that divided the hull into watertight compartments. Both Olympic and Titanic were built with fifteen bulkheads each but these did not reach the top of the hull. If more than two compartments flooded, water could flow over the top of one bulkhead and flood the next compartment.