Bulbous bow in a 15m wooden fishing boat

Discussion in 'Hydrodynamics and Aerodynamics' started by Giorgos, Sep 21, 2012.

  1. Giorgos
    Joined: Nov 2011
    Posts: 13
    Likes: 1, Points: 3, Legacy Rep: 27
    Location: Greece

    Giorgos Greek fisherman

    Hello friends.In the past i started a thread about covering a wooden boat with fiberglass.Many members helped me with that,with their opinions,and i took the proper decision about that.
    Now i need opinions about an other thing.
    I would like to know if i will gain any benefits of a bulbous bow in my fishing boat.I have post some pictures in my previous thread for those who would like to have a look before their responce.I have read in various articles for wooden bulbous bows (http://www.brayyachtdesign.bc.ca/article_bbows.html).
    I have never seen one.Has anyone in this forum see one?
    Check my thread Covering a 15m wooden fishing boat with fiberglass for pictures of my boat.
     
  2. TANSL
    Joined: Sep 2011
    Posts: 6,117
    Likes: 270, Points: 93, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    I have not seen or heard about wooden bow bulbs. But I calculated several GRP bow bulbs, which have been incorporated into various fishing vessels between 22 m and 25 m in length.
    In my country we can not increase the GRT of an existing fishing vessel. Therefore, and because of our rules, any addendum to be added to the ship `can not have a larger volume of 1 m3. As a result, the bulb is not volume, but only increases the length of the boat at the waterline: the Froude number decreases.
    My theoretical calculations say the bulb can reduce not more than 2% of consumption. This represents around 60 euros a week, that the fishermen find it very well. Furthermore, according to the fishermen, the ship is better, slightly decreasing the pitch. ????????
    You may think what you like, but this is what I know.
     
  3. Tad
    Joined: Mar 2002
    Posts: 2,303
    Likes: 185, Points: 73, Legacy Rep: 2281
    Location: Flattop Islands

    Tad Boat Designer

    The type of fishing (how you use the boat) will have huge impact on the payback from a bulb. If you run a 1000 miles to your fishing grounds the payback will be quick (assuming correct design). But if you run the boat 5 miles and stop to jig, then run back to harbour, the payback may never be seen. If you spend long periods at one throttle setting the design can be optimized for that speed, but it may be a detriment at another speed.

    Typically the bulb for a wooden boat will be bolted on and made of either steel or fiberglass. Note that some of Bray's bulbs are a piece of large metal pipe with an end cap....pretty simple.
     
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