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= Bulbous Bow Overview =
Bulbous bows were developed in the 1950’s for large cargo vessels, to improve their penetration of the water, and reduce fuel consumption. The underwater bulb creates a wave 180 degrees out of phase with the original bow wave. This cancels or reduces the bow wave. The first merchant vessel with a bulbous bow was the <i>Yamashiro Maru</i> delivered in November 1963 by the Mitsubishi Heavy-Industries, Ltd. Nagasaki Shipyard in Japan.<ref> Ripples in Time, Bulbous Bow – Introduction of wave-making resistance reduction technology, http://www.nykline.co.jp/english/seascope/200010/</ref> Today all the largest ships, including Nimitz-class aircraft carriers, have bulbs.<ref> Reagan Takes a Bow, http://www.nn.northropgrumman.com/Reagan/About_the_ship/Bow.htm</ref>
[[File:YamashiroMaru.jpg|thumb|left|260px|Yamashiro Maru -- first merchant ship with bulbous bow – Photo with permission © NYK Line, http://www.nykline.co.jp/]]
A bulbous bow will reduce fuel consumption 3% to 15%; increase sea keeping by dampening pitching motions by up to 20%; and increase speed slightly. The greatest benefit to fuel and horsepower will be at speeds over 6 knots, lessening as speed decreases.<ref>Bray Yacht Design and Research, http://www.brayyachtdesign.bc.ca/</ref> <ref>Nordhavn, http://www.nordhavn.com/design/full/bulbous.htm/</ref> <ref>Cape Horn Yachts, http://capehornyachts.com/</ref>
The <i>Yamashiro Maru</i> used 25% less horsepower than a similar vessel with no bulb.<ref>Ripples in Time, Bulbous Bow – Introduction of wave-making resistance reduction technology, http://www.nykline.co.jp/english/seascope/200010/</ref> A bulb slightly [[HullFeatures#Length on WaterlineWater Line|increases the length of the waterline]] (LWL), the determining factor in the top efficient speed of a displacement hull. A smaller boat with a bulb goes slightly faster than the LWL formula suggests.
Bulbous bows have no place on a zippy semi-displacement hull. But a full displacement boat, making a long passage at a constant speed, is an ideal candidate for a bulb. Even so, many designers have resisted bulbous bows on boats under 60 ft. But there is no good reason not to have one on displacement boats of 50 ft or even 45 ft if the hull form is suitable<ref>Bray Yacht Design and Research, http://www.brayyachtdesign.bc.ca/</ref> <ref>http://members.shaw.ca/diesel-duck/library/articles/bulbous_bows.htm/</ref> and the cruising speed is 6 kt or more. Designs by DeFever, Nordhavn, Cape Horn and Moloka’I Strait all have bulbs.
Bulb designs for large ships often incorporate a bow thruster or sonar dome. Putting the bow thruster forward as much as possible increases the steering leverage. A watertight hatch gives access to the interior of the bulb. With a bulb, you will need a bowsprit for the anchor, or hawseholes port and starboard, to avoid scraping the bulb with the anchor chain.
== References ==
[[Category:BulbousBow]]
