New Project Beam Trawler

Discussion in 'Boatbuilding' started by SixMadrid, Apr 5, 2013.

  1. TANSL
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    TANSL Senior Member

    boatbuilder41, not many people pay attention to fishing vessels, in its design, operation and management but, to me, they are very charming boats. Its forms, which is the area where most I can say, are fascinating.
     
  2. boatbuilder41
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    boatbuilder41 Senior Member

    Fishing boats are very charming, i try to encourage the ole time characteristicd of commercial boats in my new builds. Such as the one in last months NATIONAL FISHERMAN MAGAZINE. LAFITTE FOR A KING. I JUST TRY TO KEEP THE COMMERCIAL LOOK AROUND AS LONG S POSSIBLE
     
  3. SixMadrid
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    SixMadrid Marine Engineer UPM (Mad)

    Thank you for your help, Ok I am going to post my progress about my "mock project" here in this post and any help is welcome! surely your experience provides a lot of important info.

    Now I am in the first part of the project: Main Mesaures.

    So thinking about cellar capacity and oil capacity in this kind of ships, I think:

    - length range is between 25-35 meters.
    - beam range is between 6-8 meters.
    - draft range is between 2-4 meters from baseline

    And they usually have two decks: main deck between 3-5 meters from baseline, and an upper deck 2 meters over main deck.

    Any opinions about this?

    Thank you!
     
  4. SixMadrid
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    SixMadrid Marine Engineer UPM (Mad)

    I created a surface starting from the hull shared, but when I am working it in Maxsurf I can't get good results with parametric transformation.
    Despite of I like the shape a lot, although I think that bulbous is not needed because I did some calculus about my ship that I am posting in the next post.

    By the way I think that it will be useful:
    - NURBS surfaces of similar ships to parametric transformations in Maxsurf
    - General Layout of this kind of ships

    Thanks a lot!
     
  5. SixMadrid
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    SixMadrid Marine Engineer UPM (Mad)

    Ok! I did the following calculus:

    I have to transport 200 m^3 cellar (Shrimps and Octupus) and 250 m^3 marine diesel oil (MDO).And starting data is:

    -According to FAO: Frozen shrimps and Octopus have a density around 0.5 ton/m^3.

    -MDO density 0.839 ton/m^3

    How density of MDO are bigger than fish and the volume of tanks needed are more bigger than cellar, we have the critical load condition when we have 100% fuel capacity in port before going out to fish (0% fish capacity).

    So 100% fuel capacity loaded is 250 m^3 x 0,839 ton/m^3 = 210 ton

    Other loads needed:
    - Supplies = 28 ton
    - Fresh water tank 10 m^3 , density 1 ton/m^3 = 10 ton
    - Screw 125 kg/u x 8 people = 1 ton
    - Cellar Boxes = 0.75 ton
    - Food = 1.5 ton


    TOTAL 251,5 ton is my DEAD WEIGHT

    Lightship weight has been aproximated by equations checked with a based ship (MEIZOSO) as result:

    LIGHTWEIGHT =331 ton

    So DISPLACEMENT = 252,5 + 331 = 582,5 ton

    According to Gravalos studies:

    L= Coef X DISW^(1/3) x (Velocity/(Velocity + 2))^2 = 30 meters
    * Coef is experimental with based ship

    And keeping relation between L/B = 3,82 and B/Hmaindeck = 1,9

    I get: B = 7,85 m and Hmaindeck = 4,13 m

    And block coeffiecient has been aproximated by basedata and Alexandre calculus

    BC=0,69

    So Draft:

    T = DISW / (1,025·L·B·BC) = 3,5 m
     
    Last edited: Apr 10, 2013
  6. TANSL
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    TANSL Senior Member

    Here you have the file for MaxSurf, without bow bulbous.
     

    Attached Files:

  7. SixMadrid
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    SixMadrid Marine Engineer UPM (Mad)

    What is the name of this ship? In oder to have a reference to use like based ship or just to get more info?
     
  8. Adler
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    Adler Senior Member

    Question

    With all my respect is it normal to calculate the Fuel capacity at 250m³ ?
    That size is more or less 43% of total displacement.
    What will be happened with the stability on heavy seas at 25% of Fuel Capacity? and worst if they have less than 50% of max load fisheries?
    A such size of fuel quantity will tank mainly in the double bottom storage compartments.
    Take a note that the fishing equipment nets and winches are installed on main
    deck and part of them on secondary deck with a total weight near to 25-28 tons
    included the wire ropes for that size of vessel.
    A percentage of fuel capacity at 27% to 30% of total displacement could be
    managed better.
    A very sensitive point to fishing vessel design is that you obliged to avoid large changes on freeboard height because of fuel load variation.
     
  9. SixMadrid
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    SixMadrid Marine Engineer UPM (Mad)


    Yeah I agree with you, there Will be stabily problems! But I have this requiriment like a obligatory condition in the specification of the project,
    I mean 250 m^3 is needed, so I thought two things :
    - Add ballast tanks but we lost useful spaces and it is not economic
    - Increase total displacement? But we need a better engine

    Other solution? Recomendations?
    Thanks
     
  10. SixMadrid
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    SixMadrid Marine Engineer UPM (Mad)

    And What way do you take to make a previous estability calculus??
     
  11. TANSL
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    TANSL Senior Member

    If we understand that a boat is stable when easily meets the criteria for that type of boat, can occur that the boat is more stable half load than full load. You only need to avoid the effect of free surface, but that is an issue that is usually not a problem.

    As far as I know, there is no stability criterion nor any regulation (safety, pollution, ...) requiring to avoid large variations in freeboard.
     
  12. Adler
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    Adler Senior Member

    Points to clarify.

    Regarding the points you mentioned you are right and of course that will be
    happened when everyone will make the study and the calculations when the
    vessel float or run.
    The points that noted are related to the special job of this kind of vessel.
    A trawler more than usual hydrostatics has to react on davits' forces specially
    at the moment when the winches rapidly will heave wire ropes and nets to the deck and then often one of the ropes will be caught at sea bed or broken
    through high dynamic load.
    My concern was just to be involved these factors into account of the study
    and not to indicate a fault but tried to note two parameters ( fuel volume and
    freeboard level changes) that are involved to change rolling torque in such cases.
     
  13. TANSL
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    TANSL Senior Member

    Adler, everything you say is very reasonable but not only in fishing but in any ship, you need always consider the worst loading condition and study its stabilityt. For trawlers and purse seiners, the worst condition often occurs with, let's call it, "the last load" that the boat performs. That is the last time the boat up the network, full loaded, hanging of the blocks. This study is not recommended, but is mandatory and any designer must know and apply. That condition or any other that, in his boat, give rise to adverse situations.
    As the load line, the only thing is to take care not to immerse the maximum freeboard line.
    What the OP is doing, probably, is his final career project. It may be that his project specifications are very close to the limits of reason. Even if the boat is impossible, the student must realize and communicate this circumstance.
     
  14. Adler
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    Adler Senior Member

    Hopefully yes.
     

  15. rxcomposite
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    rxcomposite Senior Member

    Why not? It is a good idea if the parameters fits. These trawlers are in the category of special ships. Low L/D ratio, high Cb, overdriven hulls which needs to get to its destination quickly because of perishable goods.

    Outbound, it is heavily laden with fuels, provisions, and bait. As it is consumed it is replaced with catch, keeping the displacement more or less constant.

    So for a Fn range of about 0.238 to 0.30 where bulbous bow is beneficial, it will work.
     

    Attached Files:

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