Anchor design

Discussion in 'Boat Design' started by milad.naval, Nov 21, 2010.

  1. milad.naval
    Joined: May 2010
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    milad.naval Junior Member

    Hi,
    I have got a university homework that I should choose an anchor for a composite boat. I calculated the equipment number (E.N=21) with dnv rule for hsc but I can't found the suitable anchor because it's not included.Could any one help me?
    Thanks a lot.
     
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  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    What is equipment number? Anchors are selected according to sea/wind conditions and type of bottom.
     
  3. Submarine Tom

    Submarine Tom Previous Member

    The bottom type is crucial. Rock, mud, sand, shale, heavy weeds or kelp cover...

    -Tom
     
  4. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    Gonzo, you said that you are a surveyor?.......Equipment Number is a calculation that takes into account the profile of a vessel in relation to its above waterline areas and its displacement...have a look at your standards for say, Lloyds. It will be described therein.
     
  5. milad.naval
    Joined: May 2010
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    milad.naval Junior Member

    hello,
    thanks for your replies,i calculated equipment number by dnv, it is 21 but my problem is that the equipment number is fewer than base equipment number that dnv mentions on it. the base equipment number of dnv is 30,i think bottom type is sandy.
    thank you all.
     
  6. Craig Smith
    Joined: Nov 2010
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    Craig Smith Anchorsmith

    Are you required to meet DNV Rules for your vessel or are you just assuming this is the appropriate way to proceed? It seems like a small boat to be going through certification.

    If you require adherence to Rules, then as you are aware they typically do not provide anchor sizing for EN < 50. They're generally not interested in certifying anchors much under 100 kg. However, the Rules say that you can interpolate sizes for EN #s not listed in the tables. For an EN of 21 you might therefore get:
    - A standard anchor of 76+ kg, or
    - An HHP anchor of 57+ kg, or
    - An SHHP anchor of 38+ kg
    You would have to get the classification society to agree with this rationale.

    If you don't require classification then the above is a decent guide to start with, but you should probably make your own decisions based on the properties of the boat. For advice from the likes of Rocna they would want to know the LOA and displacement of the vessel. For example consider their sizing advice:
    www.rocna.com/kb/Rocna_sizing_recommendations
     
  7. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    I was under the impression that Ford engines makes the best anchors for any conditions and bottoms... :rolleyes:

    Modern anchors makes for superior holding as Craig advised, Rocna is one of them.
     
  8. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Ford engines the best anchors..YOU CRAZY !!! youre gonna loose your boat, everyone knows Mercury outboard motors have twice the holding power and neatly nest on your stern rail when not being used in anchor mode .
     
  9. milad.naval
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    milad.naval Junior Member

    Thank you Craig Smith
     
  10. Alik
    Joined: Jul 2003
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    Alik Senior Member

    Take any equioment catalog, say Westmarine, and choose from there depending on length. Equipment number is too formal way to choose anchor for such a small boat.
     
  11. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Northill was and is the best anchor for its size. They are hard to get however.... I am sure many will disagree. Danforths are not worth the metal they are made from.
     
  12. Submarine Tom

    Submarine Tom Previous Member

    Well that's a pile of stinky. My 14 pound, used danforth was $20US and out of the six styles I've used in this area, is the absolute best.

    What ground material are you anchoring in mydauphin?

    -Tom
     
  13. michael pierzga
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    michael pierzga Senior Member

    Both Danforth and fisherman are very valuable because they store flat. This means you can carry a huge danforth as a backup, kedge.
     
  14. garydierking
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    garydierking Senior Member

    I agree about the Northill, but are they still produced?
     

  15. michael pierzga
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    michael pierzga Senior Member

    I rarely see them. Great anchor. . They are difficult to store on the stem. Perhaps google it.
     
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