A ship designer wants a fine, fast vessel. Which form coefficient would they specifically aim to make smaller to achieve this?

A ship designer aiming for a fine, fast vessel would specifically aim to make the Block Coefficient (Cb) smaller. The Block Coefficient is a non-dimensional form coefficient that quantifies the overall fullness of a ship's underwater hull. It is calculated as the ratio of the ship's actual underwater volume (the volume of water displaced by the hull) to the volume of a hypothetical rectangular block that shares the same maximum length, maximum breadth, and maximum draft as the ship. In essence, it describes how much of the bounding rectangular box the ship's submerged hull occupies. A "fine" vessel refers to one with a slender, streamlined hull form, characterized by narrow, tapering ends (bow and stern). This shape is crucial for minimizing resistance as the vessel moves through water. A "fast" vessel is designed to achieve high speeds efficiently, which inherently demands the lowest possible resistance. By making the Block Coefficient smaller, the designer ensures that the ship's underwater hull takes up a significantly smaller proportion of its theoretical rectangular block. This translates directly to a more slender and less voluminous hull shape overall. A smaller Cb indicates a "finer" hull, meaning it has gentler curves and less bulk, especially at the bow and stern. This reduced fullness is vital because it significantly decreases the amount of water the ship has to push aside, thereby reducing the resistance it experiences. Crucially for fast vessels, a smaller Cb effectively minimizes wave-making resistance, which is the energy lost to creating waves as the ship moves. A finer hull generates smaller, less disruptive waves, allowing the vessel to move through the water with less effort and achieve higher speeds using less power.