Main Deck Design for Towing Winch Sitting

Discussion in 'Boat Design' started by siakeeho, May 13, 2009.

  1. siakeeho
    Joined: Aug 2008
    Posts: 1
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Sarawak,Malaysia

    siakeeho New Member

    Hi, currently i was given a task to calculate and design the main deck structural for 31m tug boat. How do i calculate the scantling for the main deck stiffeners especially on the area where the towing winch is located.
  2. apex1

    apex1 Guest

    First, I would say, you do it yourself, then I would add, at least sufficient.
    It seems to be a better approach to do your work first and ask for comments or corrections than to ask others to do the job.

  3. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 491, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Calculate the loads imposed, add a suitable safety margin that is client acceptable and satisfies regulatory requirements and hope they don't max it out during normal use.
  4. apex1

    apex1 Guest

    Or that way, yes.
    But do it yourself.

  5. McFarlane
    Joined: Apr 2009
    Posts: 20
    Likes: 0, Points: 0, Legacy Rep: 3
    Location: Australia

    McFarlane Macka

    Depends on the length, beam and wieght of the tug and how much wieght the tug is expected to tow, its a bit like the tow point of a car, the tow point must be married to the shasie of the vessel to enshure maximum towing strength.
    PS Hi apex sorry I didnt check with u before my comment but it sounds like you cant answer the question. : )
  6. apex1

    apex1 Guest

    Jaja Macka, but you did?

  7. tobbe
    Joined: Nov 2007
    Posts: 6
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Sweden

    tobbe Junior Member

    To assist you in the area around the towing winch I qoute what DNV states in their rules what loads to apply. Basically it says that a SF of 1.25 times the maximum load or the towing line breaking load should be used. I use the breaking load, see at the end, for designing the supporting hull structure, to make the line the weakest link.

    Unless greater safe working load (SWL) of shipboard fittings is specified, the minimum design load to be used is the following value of (1) or (2), whichever is applicable:
    (1) for normal towing operations (e.g. in harbour / maneuvering), 1.25 times the intended maximum towing load (e.g. static bollard pull) as indicated on the 'Towing and mooring arrangement plan'.
    (2) for other towing service, the nominal breaking strength of the towing line according to values given as guidance in Sec.3 Table C1, for the ship's corresponding equipment number.
    The breaking loads of towing lines given as guidance in Sec.3 Table C1 is the design load to be applied to the shipboard fittings and supporting hull structure.
    The design load is to be applied through the tow line according to the arrangement shown on the 'Towing and mooring arrangements plan'.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.