What is a Bulbous Bow?

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Earlier today I was talking to my dad who is a retired harbor pilot. See earlier post on river/harbor pilots. 
We were talking about the different bow configurations of cruise ships and why some ships have bubbles on the bows (front of ship). Skating around the whole physics part of the bow bubble (bulbous bow the technical term) I asked me dad a few questions.
 
Wikipedia describes the Bulbous Bow: a protruding bulb at the bow (or front) of a ship just below the waterline.
 
Bulbous Bow

A Bulbous Bow (yachtforums.com)

 
Questions and Answers:
 

What exactly does the bulbous bow do? The bubble breaks the friction between the ocean and the steel of the ship.  In return, the ship is more fuel efficient and cuts through the water more smoothly. 

What kind of material is it made of? The same type of material the hull of the ship is made of, steel. 

What kind of ships have a bulbous bows?  Passenger, container ships, car ships, military…. mostly any ship that draws more than 15 ft of water.

How long have they been around for? Most ships that were built in the 1980′s to current have these bubbles installed on them. The bubbles were used in early as the 1930s but were known as experimental.

You mentioned the bulbous bow is fuel efficient, how so?  Depending on the metrics of the ship it can reduce the drag through the water up to 15%. Less drag, less friction, less fuel usage.   

How deep does the bulbous bow go? The bubble goes down to the keel (bottom) of the ship.

Can a harbor tug hit the bulbous bow if it gets to close to it? Yes, and when it does, it will shake the whole ship …. steel touching steel is not good.

Could a tug hitting it compromise the integrity of the hull?  Of course, any outside force can. Look what a sheet of ice did to the titanic.

 Thanks for the answers!
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Comments

  1. Glenn Brotherton says

    Good concise explanations. Logical replies.
    I wish to point out (1) A grammatical error on one of the above questions: “Do type of ships” should be “What type of ships. . .”
    and (2) I wish that you had a dozen little photos showing everything from fishing boats, long range cruisers, super-tankers, aircraft-carriers, coast guard vessels,
    luxury liners, cargo ships and sailboats with bulbous bows. I think your brief presentation with various photos would would outrank many larger, more technical ariticles. Thanks for your efforts.

  2. admin says

    Thanks so much for pointing out my error and reading, Glenn. Sometimes I get so excited typing that my fingers move faster than my brain.

  3. Andrew says

    Interesting basics, one major and probably the most important benefit these provide has been left out.

    The bulb redirects the bow wake to pass more flow over the area of the prop at the stern causing a huge jump in fuel efficiency. 30%+

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