Bulb flat profile

A bulb flat is a rolled stiffener with a flat web and an asymmetric rounded bulb along one edge, designated HP (Holland Profile) by web height in millimeters, from about HP80 to HP430 with web thickness 4 to 20 mm. The bulb concentrates material at the free edge to raise the section modulus and resist tripping without the labor of a welded face plate, so it replaces a built-up T-bar or flat bar for secondary stiffening of plating: shell longitudinals, deck and bulkhead stiffeners. The single rolled section welds with one fillet line per side, faster than fabricating a flange-stiffener, which is why it is the default light stiffener in merchant hull construction.