Bulbous bow A bulbous bow is a protruding bulb at the bow ( or front ) of a ship just below the waterline . The bulb modifies the way the water flows around the hull , reducing drag and thus increasing speed , range , fuel efficiency , and stability . Large ships with bulbous bows generally have a twelve to fifteen percent better fuel efficiency than similar vessels without them . A bulbous bow also increases the buoyancy of the forward part and hence reduces the pitching of the ship to a small degree . Bulbous bows have been found to be most effective when used on vessels that meet the following conditions : Thus , large vessels that cross large bodies of water near their best speed will benefit from a bulbous bow . This would include naval vessels , cargo ships , passenger ships , tankers and supertankers . All of these ships tend to be large and usually operate within a small range of speeds close to their top speed . Bulbous bows are less beneficial in smaller craft and may actually be detrimental to their performance and economy . Thus , they are rarely used on recreational craft like powerboats , sailing vessels , tug boats , fishing trawlers and yachts . How it works . In a conventionally shaped bow , a bow wave forms immediately before the bow . When a bulb is placed below the water ahead of this wave , water is forced to flow up over the bulb . If the trough formed by water flowing off the bulb coincides with the bow wave , the two partially cancel out and reduce the vessel ' s wake . While inducing another wave stream saps energy from the ship , canceling out the second wave stream at the bow changes the pressure distribution along the hull , thereby reducing wave resistance . The effect that pressure distribution has on a surface is known as the form effect . Some explanations note that water flowing over the bulb depresses the ship ' s bow and keeps it trimmed better . Since many of the bulbous bows are symmetrical or even angled upwards which would tend to raise the bow further , the improved trim is likely a by - product of the reduced wave action as the vessel approaches hull speed , rather than direct action of water flow over the bulb . A sharp bow on a conventional hull form would produce waves and low drag like a bulbous bow , but waves coming from the side would strike it harder . Also , in heavy seas , water flowing around the bulb damps pitching movements like a squiggle keel . The blunt bulbous bow also produces higher pressure in a large region in front , making the bow wave start earlier . The addition of a bulb to a ship ' s hull increases its overall wetted area . As wetted area increases , so does drag . At greater speeds and in larger vessels it is the bow wave that is the greatest force impeding the vessel ' s forward motion through the water . For a vessel that is small or spends a great deal of its time at a slow speed , the increase in drag will not be offset by the benefit in damping bow wave generation . As the wave counter effects are only significant at the vessel ' s higher range of speed , bulbous bows are not energy efficient when the vessel cruises outside of these ranges , specifically at lower speeds . Development . Although the bulbous bow concept is credited to David W . Taylor , a naval architect who served as Chief Constructor of the United States Navy during the First World War and who used the concept ( known as a bulbous forefoot ) in his design of the , which entered service in 1910 , there are earlier examples . Models in the Discovery museum , Newcastle - upon - Tyne , England of several warships built in Newcastle during the last decade of the 19th century , ( Notably in the yards of William Armstrong , 1810 - 1900 ) show bulbous bows . An illustration of the cruiser USS Albany ( launched 1899 ) which appears in the biography of Armstrong by Henrietta Heald ( 2010 ) appears to show a bulbous bow . It may be of relevance that Armstrong was a hydraulics engineer . The bow design did not initially enjoy wide acceptance , although it was used in the to great success after the two ships of that class which survived the Washington Naval Treaty were converted to aircraft carrier s . This lack of acceptance changed in the 1920s , with Germany ' s launching and . They were referred to as Germany ' s North Atlantic greyhounds , two large commercial ocean liners that competed for the trans - Atlantic passenger trade . Both ships won the coveted Blue Riband , the " Bremen " in 1929 with a crossing speed of , and the " Europa " surpassing her in 1930 with a crossing speed of 27 . 91 knots . The design began to be incorporated elsewhere , as seen in the U . S . built " SS Malolo " , " SS President Hoover " and " SS President Coolidge " passenger liners launched in the late 1920s and early 1930s . Still the idea was largely viewed as experimental by many ship builders and owners . In 1935 the French superliner coupled a bulbous forefoot with massive size and a redesigned hull shape . She was able to achieve speeds in excess of 30 knots ( 56 km / h ) . The " Normandie " was famous for many things , including her clean entry into the water and markedly reduced bow wave . " Normandie " s great rival , the British liner , achieved equivalent speeds with a non - bulbous traditional stem and hull design . However , a crucial difference was that " Normandie " achieved these speeds with approximately thirty percent less engine power than " Queen Mary " and with a corresponding reduction in fuel use . Bulbous bow designs were also developed and used by the Imperial Japanese Navy . A modest bulbous bow was used in a number of their ship designs , including the light cruiser and the carriers and . A far more radical bulbous bow design solution was incorporated into their massively large , including , and the aircraft carrier . The modern bulbous bow was developed by Dr . Takao Inui at the University of Tokyo during the 1950s and 1960s , independently of Japanese naval research . Inui based his research on earlier findings by scientists made after Taylor discovered that ships fitted with a bulbous forefoot exhibited substantially lower drag characteristics than predicted . The bulbous bow concept was first definitively studied by Thomas Havelock , Cyril Wigley and Georg Weinblum , including Wigley ' s 1936 work " The Theory of the Bulbous Bow and its Practical Application " which examined the issues of wave production and damping . Inui ' s initial scientific papers on the effect of bulbous bow on wavemaking resistance were collected into a report published by the University of Michigan in 1960 . His work came to widespread attention with his paper " Wavemaking Resistance of Ships " published by the Society of Naval Architects and Marine Engineers in 1962 . It was eventually found that drag could be reduced by about five percent . Experimentation and refinement slowly improved the geometry of bulbous bows , but they were not widely exploited until computer modelling techniques enabled researchers at the University of British Columbia to increase their performance to a practical level in the 1980s . Sonar domes . Some warships specialized for anti - submarine warfare use a specifically shaped bulb as a hydrodynamic housing for a sonar transducer , which resembles a bulbous bow but the hydrodynamic effects are only incidental . The transducer is a large cylinder or sphere composed of a phased array of acoustic transducers . The entire compartment is flooded with water and the acoustic window of the bulb is made of fiber - reinforced plastic or another material ( such as rubber ) transparent to underwater sounds as they are transmitted and received . The transducer bulb places the sonar equipment at the greatest possible distance from the ship ' s own noise - generating propulsion system .