equipment number

Discussion in 'Class Societies' started by navalarchitect, Apr 2, 2013.

  1. navalarchitect
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    navalarchitect Junior Member

    how can i choose an anchor if the equipment number is less than the value listed by class in the table? i'm getting 10-15 en.
     
  2. Ad Hoc
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    Ad Hoc Naval Architect

    Double check your calc's...failing that, just use the minium shown.
     
  3. navalarchitect
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    navalarchitect Junior Member

    for 14.5m patrol boat. I doubled check. Using DNV I got 15.4 while 15.1 in BV. DNV has anchor selection for EN 30 up whiel BV has EN 19 up.
     
  4. Ad Hoc
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    Ad Hoc Naval Architect

    You cannot cherry pick or mix/match EN results calc's from different Class rules. Use one or the other...comparing one to another is also meaningless.
     
  5. rxcomposite
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    rxcomposite Senior Member

    EN's differs from class to class. Here is something from my old calculation that maybe will make things easier for you. Just fill in the yellow cells and the blue cell will calculate.

    By the way, are you using the subset of DNV rules? For Patrol Boats, we were given a separate rule book aside from the DNV general rule book.
     

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  6. navalarchitect
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    navalarchitect Junior Member

    Yes. I use DNV Rules for Patrol Boats.

    I have also the calculation written in excel. You need to correct the formula (C2^2/3) to C2^(2/3).
     
  7. rxcomposite
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    rxcomposite Senior Member

    Sorry I posted the wrong version in haste. Should have deleted that autosaved version a long time ago. My apology.
     
  8. TANSL
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    TANSL Senior Member

    I do not know if it will help you but I would attach some calculations I did for a patrol boat of 16 m, according to the "Special Service Craft Rules" of Lloyd's Register. I believe that the differences between the various classification societies exist, but they can't be great.
     

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  9. navalarchitect
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    navalarchitect Junior Member

    my problem is not getting the equipment number but the weight of the anchor to use because the equipment number i get is 15 which you cannot see in the anchor selection table.
     
  10. TANSL
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    TANSL Senior Member

    What I have tried to show is that a boat of 14 m, with two decks, it is difficult to have a so small EN. I think you should check your calculations. But only an opinion, of course, since I have no data, displacement, windage area, etc. of your boat. I tried to give you information that you compare your results with those of a similar boat.
    If you want, and give me the information, I will calculate your boat to analyze what is happening.
    I've calculated boats 7 m in length, one deck, which EN was inside the table values for anchor selection.
     
  11. Alik
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    Alik Senior Member

    Take Rules for yachts and boats below 24m in length from GL, they have a nice feature in tables for anchor weight - they do show both equipment number and displacement of boat, so You can use either to choose anchor weights and validate the results.
     
  12. rxcomposite
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    rxcomposite Senior Member

    Check again your restriction code. You mentioned "Patrol Boat" so it automatically rules out "Naval Vessels" hence you must be operating in the R2 to R3 operating range which is offshore or coastal. Your design could even be R4, R5, or R6 (inshore, inland, sheltered) depending on the tonnage and operation. What is your SOR? Give us more information.

    Section C2 allows up to 30% reduction of mass on type 1 equipment and up to 50% reduction on type 2.

    Therefore, with the minimum listed mass of anchor of 93 kg. for EN 30-39, you are allowed to reduce the mass. Further, note that the minimum mass listed by DNV for proof test is 50kg. Much lower than what you will get if you reduce the 93 kg by 30%. There is also reduction if you use 2 anchors.
     
  13. TANSL
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    TANSL Senior Member

    With data from your boat I get an EN = 14.8. Similar to what you get.
    Attached is an excerpt from the table that the SSC of Lloyd's has to select the anchor weight based on the value of EN. The table allows to select anchor for EN values ‚Äč‚Äčeven under 5.
    Then, depending on the correction factor, you can reduce the weight of your anchor.
    I know you have to use another regulation, but it might help contemplating the SSC.
    Cheers.
     

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  14. rxcomposite
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    rxcomposite Senior Member

    I agree with TANSL. Small boat. I am getting this.
     

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  15. navalarchitect
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    navalarchitect Junior Member

    Thanks I need to get a copy of the SSC rules...Unfortunately there's no free pdf download.
     
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