tugboat: newbie level

Discussion in 'Boat Design' started by Shakes, Sep 2, 2012.

  1. Shakes
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    Shakes Junior Member

    Hey, guys. How do I find the particulars for a harbor tugboat? I mean what's the first step in designing one?
     
  2. rasorinc
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    rasorinc Senior Member

    check out the tugs on the Glen-L site
     
  3. Shakes
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    Shakes Junior Member

    Thanks! but I was planning on it being around 30 to 40 meters. With a speed of 15knots. :D
     
  4. rasorinc
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    rasorinc Senior Member

    If this is going to be a full size working tug with 2=1,000 HP engines then the first thing I would do is hire a Naval Architect. This type of design is not for amatures.
     
  5. ldigas
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    ldigas Senior Member

    Usually boats are designed/built based on previous designs which have proven reliable, by changing (improving, hopefully) a few things which have not.

    So your first step would probably be to make a small "database" of similar tugs, which will give you a rough estimation of the design parameters (particulars amongst others), then start from one of them and go on from there.
     
  6. Shakes
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    Shakes Junior Member

    Well, I guess my topic title is a bit misleading. Actually, I'm studying Naval Architecture and wanted to try designing a tugboat. Just the preliminary design, at least.


    thank you!!! you wouldn't happen to know any books I could read? :)
     
  7. PAR
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    PAR Yacht Designer/Builder

    Why yes, try your text books and consider a simpler project, as 100' vessels aren't for novices.
     
  8. Shakes
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    Shakes Junior Member

    we don't have textbooks. Most of our knowledge comes from our professors and whatever can siphon off the internet. :(
     
  9. Tad
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    Tad Boat Designer

    First step is to find comparables and learn from them. The School Library is the place to start, professional journals often publish design drawings.

    Below is the Robert Allan Ltd design Oita, a fire-fighting escort tug for Western Australia. She is 32m by 11.6m, draft is 5.66m, displacement 856 tonnes, max speed is 13 knots.

    RAtug.jpg
     
  10. Shakes
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    Shakes Junior Member

    Thank you, sir!

    Just a question though. Suppose I want to make my own design with its own length and such, do I just get the mean/average from the parentships' particulars?
     
  11. Tad
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    Tad Boat Designer

    Best to set up a spreadsheet and reduce particulars to dimensionless ratios; beam/length, beam/depth, beam/draft, displacement/length, HP/cubic number, etc........
     
  12. rxcomposite
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    rxcomposite Senior Member

    Here are the coefficients and trial dimensions.
     

    Attached Files:

  13. Shakes
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    Shakes Junior Member

    Do I have to use formulas to determine length?

    thank you. :)
     
  14. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    You are approaching it the wrong way. You are designing for a harbor tug so the first thing you should do is define the size of the vessel you are going to assist and the limiting weather condition you will be operating. Displacement of the vessel to be towed is not enough. Remember, a bulk tanker is mostly weight under the water (weight, with very little volume above water) but a passenger ship is great volume above water creating a lot of wind resistance with little underwater volume.

    Next find Hp. needed. You can search in this forum for "Bollard Pull" as discussed by Guillermo and Ad Hoc, two of the most respected member of this forum. Find the Hp. needed as shown in the formula.

    Knowing the Hp, you can calculate for the weight of the propulsor. A medium speed diesel is about 0.013 tonnes/Kw or 50 to 100 Kw/ton.

    A harbor tug is nothing but a very big engine on a tub. You will have very little deadweight as you will have no cargo. Calculate the fuel needed for operation, the crew size needed for the vessel, fresh water consumables, crew's effects and provisions. By proportion, this will be very small for the size of the vessel.

    Next, tabulate the weight of the tugboat broken down into:
    Lightship
    1. Structure
    2. Propulsion
    3. Electrical
    4. Communication
    5. Auxilliary
    6. Outfit
    7. Armaments (ommitted)

    Deadweight:
    1. Cargo (ommitted)
    2. Crews and effects
    3. Provisions
    4. Fresh Water
    5. Fuel Oil

    Add the two sub groups and you have your displacement weight.

    By ratio and proportions, guided by the coefficients, you will get a length by which you will be able to calculate your hull speed.
     

  15. Submarine Tom

    Submarine Tom Previous Member

    Without a purpose to design to then anything with props that floats will do.
     
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