Towing Hook Tug Boat for 330 feet barge

Discussion in 'Props' started by Hendrickj, Jun 25, 2012.

  1. Hendrickj
    Joined: May 2012
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    Location: West Java

    Hendrickj Junior Member

    Dear Mr/Mrs,

    Good Morning,

    We have Tug Boat for towing Barge which operated at river.
    Tug Boat have 2 x 829 HP, and 15 ton Towing Hook cap.

    Anyone have suggestion, whether our tug boat can tow the Barge 330 feet 7500 ton DWT ? Whether the towing hook is safe for that operation.

    Thanks.

    Regards,
    Hendrik Kurniawan.
     
  2. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Hi Hendrik,

    As a rough guess, if you assume the very best coeff of friction of the Barge in the water is say 1%, very low, to move, so almost like on ice, that equates to 75 tonne required to pull. So I would say 15 tonne is rather light!

    In reality the coeff could be more like 3-5%, taking into account debris in the water, rough hull bottom, bluff shape etc. etc., without knowing any more details.

    However, you also wish to read here:
    http://www.boatdesign.net/forums/boat-design/required-bollard-pull-harbour-tug-24572.html#post563542
     
  3. Hendrickj
    Joined: May 2012
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    Location: West Java

    Hendrickj Junior Member

    Dear Mr. Ad Hoc,

    Thank you, we have already read that chapter.
    However, The Bollard Pull is about BHP/100 (rough estimated). So, what about towing hook ? Do you have formula for that ? because we read at propeller handbook ( Dave Gear ) and we can't find that formula.

    And our crew at Tug boat is worried if they use 15 ton towing hook to tow the 300 feet Coal Barge.

    Thank you for your knd assistant.
     
  4. Ad Hoc
    Joined: Oct 2008
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    Location: Japan

    Ad Hoc Naval Architect

    Hendrik,

    Another way to look at it would be, what would the drag be at say 5~10 knots of the barge?...as if a towing tank calculation.

    Well, length = 100m, and these barges are usually around L/B of 5, so a beam of roughly 20m. Thus what is the draft...well, say a Cb of 0.90, it is almost like a block, which equates to a draft of roughly 4.2m.

    From this a rough box can be assumed gives a WSA of roughly 2880m^2.

    So, working out the Rn number at say 5 knots of towing what would the frictional drag/force be?

    5 knots = 18.27kN
    7 knots = 34.22kN
    10 knots = 66.61kN

    If you then add say 20% for residuary, even though Fn is low, then the values of force at say 10knots is 8 tonne. But would be nice to get some handle on residuary of such a slow heavy boat, it could add up!!

    So, ignore the rubbish I posted above..hahaha...it was a pure guess.

    So, your barge towing hook of 15tonne should be ok....but, what is the SWL, is it 15 tonne or a max of 15 tonne?

    Ive just dug out an old tank test I did for a dutch barge. If i pessimistically use the same value but doubled, (as more stream line hull shape) i get roughly 0.01kN/tonne at this speed range = 75kN, a bit more than 20% of frictional. As the total is now 75+66 = 141kN roughly 14 tonne...so, actually close!
     

  5. Hendrickj
    Joined: May 2012
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    Location: West Java

    Hendrickj Junior Member

    Mr. Ad Hoc,

    We use Tug Boat with :
    LOA : 26 m
    Bmld: 8,0 m
    H : 3,65 m
    T : 3,00 m

    Engine : 2 x 829 HP
    G/B : 5,91
    Prop : 1800 mm (diam).

    And our calculation is we used Bollard Pull formula from Propeller Handbook and we get 11,96 Tonnes Bollard Pull. And for the Towing hook is we times the Bollard Pull with (1,1 - 1,3), and we get 14,35 Tonnes Towing Hook.

    In yard, our Tug installed with 15 Ton Capacity and Proof Capacity is about (15 - 30) Tonnes. Hope this capacity is sufficient and safe for 300 feet barge operation.
     
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