Entrance angle (half angle of entrance, iE)

The half-angle of entrance, iE, is the angle between the design waterline at the bow and the ship’s centerline, measured to one side, so it describes how sharply or bluntly the waterline opens out from the stem. A small iE gives a fine entrance that pushes water aside gently and lowers wave-making resistance; a large iE marks a full, blunt bow typical of tankers and bulkers that accept higher wave resistance for cargo volume. iE is a direct input to resistance methods: Holtrop-Mennen uses iE in its wave-resistance terms, and where it is not given it is estimated from CB, LCB, and the length-beam ratio. Designers fair the forward waterlines to the target iE.