Why Ships Have a Hidden Nose, and Why Some Owners Cut It Off

Why do large ships carry a bulbous bow, a rounded bulb below the waterline, and why did Maersk and other owners pay to cut theirs off in 2013? The bulb only saves fuel when it is tuned to the speed the ship actually sails. The bulb makes a wave of its own, timed so its trough lands under the bow's crest and flattens it. Speed sets the length of a ship's waves, so that timing works only near the design speed. When container ships slowed from about twenty-five knots to the mid-teens after 2008, many bulbs fell out of tune and mostly added friction. We follow the bow refits in Qingdao, a measured result from another owner, and the history from warship rams and USS Delaware to Takao Inui's wave-cancelling designs. Diagrams are simplified illustrations. Fuel-saving figures for the refits are company-reported estimates or short-term measurements. #Ships #NavalArchitecture #Shipping #HowItWorks