damage case problem- hydromax

Discussion in 'Software' started by bam_yat, Apr 12, 2013.

  1. bam_yat
    Joined: Sep 2011
    Posts: 25
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: malaysia

    bam_yat Junior Member

    I have problem in running the analysis of damage case.
    if the boat has ramp at the fwd part and i want to show the flooding condition at main deck, should i set the main deck as another compartment or left it as open deck?because in that loading condition, there is a cargo weighing 5 tonne fwd the midship.i tried to run both ways, but the results really different.which one is correct actually?
     
    Last edited: Apr 12, 2013
  2. hoytedow
    Joined: Sep 2009
    Posts: 5,402
    Likes: 195, Points: 73, Legacy Rep: 2489
    Location: North of Cuba

    hoytedow Wood Butcher

    Please attach a picture of the area in question. It is a good way to make your question easier to understand.
     
  3. bam_yat
    Joined: Sep 2011
    Posts: 25
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: malaysia

    bam_yat Junior Member

    Here I attach the pictures of 3D and damaged compartment that i set.by looking to the picture, i saw that the water level is already exceed the main deck which the water can go in through the ramp.
     

    Attached Files:

  4. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Is the ramp a watertight joint?

    Is the main deck above or below the ramp?

    Is the main deck watertight throughout its length?
     
  5. bam_yat
    Joined: Sep 2011
    Posts: 25
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: malaysia

    bam_yat Junior Member

    the ramp is not watertight joint.
    main deck is at the same level with the ramp.
    main deck is watertight.
     
  6. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    The joint of the ramp to the main deck, this is a hinged joint of some type, is that correct? Does this joint penetrate the main deck, to allow the ramp to be flush with the main deck when deployed?..or is there a small 'step', thus the 'hinge' is above the main deck and does not penetrate the main deck structure?
     
  7. bam_yat
    Joined: Sep 2011
    Posts: 25
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: malaysia

    bam_yat Junior Member

    based on the GA, it's a hinged joint,penetrate to the main deck.is the joint give any difference to the result?so, i should set it as compartment or any correct way?
     
  8. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    If the joint penetrates the main deck and is not watertight joint, then you already have "lost" buoyancy when the hull is damaged!

    You are only looking at the hull, and if the hull, or part of the hull you are investigating is open to the atmosphere, then it makes the dame scenario much worse. Since in a seal void, the air is being pressed as the vessel sinks and eventually reaches a maximum. Yet with an "open" or ventilated void, it shall keep filling up with water until the remaining buoyancy of the undamaged hull can support the "lost" buoyancy.

    In addition, the freeboard is compromised too, if the penetration is below the main deck. Since the damage has an assumed length and vertical height.

    Thus you need to ensure the hinged joint does not compromise the damage stability conditions when the void(s) are flooded.
     
  9. TANSL
    Joined: Sep 2011
    Posts: 5,803
    Likes: 203, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    The first thing to know, regardless of the closing of the bow ramp, is that no damage case in the boat must get the "margin line" (a line parallel to the deck, below it) under the wáter line. As seen in your figures, the ship does not comply. No need, for now, to worry about the tightness of the ramp. Before you fix the problem with "margin line". I think, without any calculation, you should increase the freeboard and reduce the length of the compartments.
     
  10. bam_yat
    Joined: Sep 2011
    Posts: 25
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: malaysia

    bam_yat Junior Member

    actually, i just need to show that the design is not safe.the problem is i didn't know whether i need to set the main deck as compartment or not.
     
  11. Ad Hoc
    Joined: Oct 2008
    Posts: 6,168
    Likes: 399, Points: 83, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Forget about the margin line. That is only on big ships, not small boats like yours.

    You have already answered your own question. Which is why I asked you the questions in a particular way, to see if you could work it out.

    Ergo, anything above the main deck is "open"....i.e. ignore, it is not part of the hull. The bulwark only serves to act as increasing the angle at which progressive flooding takes place. Unless of course the bow/ramp is already immersed, since it is not watertight, as you have noted above, in which case makes no difference, ignore the bulwark. But that is for you to prove :)
     
  12. TANSL
    Joined: Sep 2011
    Posts: 5,803
    Likes: 203, Points: 73, Legacy Rep: 300
    Location: Spain

    TANSL Senior Member

    bam_yat, if you define a deck as the "Main Deck", it must be watertight. So everything below it, limited by transverse bulkheads is a compartment. Depending on the number of transverse bulkheads will be more or less number of compartments. If any of them is too large, by flooding it, will occur immersing the margin line.
    In your case, in view of the figure, the boat does NOT meet stability after damage.
    If you want to solve the problem, it is possible that adding the forepeak bulkhead (which is probably required), have the solution.
     

  13. bam_yat
    Joined: Sep 2011
    Posts: 25
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: malaysia

    bam_yat Junior Member

    i got that idea..thanks to all..:)
     
Loading...
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.