Where to find holding factor for anchor?

Discussion in 'Boat Design' started by floating, Mar 22, 2016.

  1. floating
    Joined: Jun 2009
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    floating Junior Member

    A colleague said he expects a 1 metric tonne Danforth anchor in sand to have a 1:20 holding factor, and I'd like to understand where this information comes from (I'm new to anchor selection). Where can I find a lookup table for holding factors for different seabed types?
     
  2. floating
    Joined: Jun 2009
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    floating Junior Member

    Found this reference,
    http://wetlands.simplyaquatics.com/d/14871-1/App_g.pdf
    For our Danforth anchor which weights 1 metric tonne (2204 lbs), the plot in Fig G7 predicts a ~35,000 lb holding capacity for a Danforth anchor in sand (left plot), so holding factor is 35,000/2204 = 1:11. Does that calculation make sense?
     
  3. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    MIL-HDBK-1026/4A (eq 26 and Table 34) says 167.05 kN (~17046 kg or ~17:1) for a 1 tonne Danforth in sand when set to the manufactures recommended fluke angle for sand. Note that the equation is not linear so the holding factor is not constant. To understand the why of this you will need a good geotechnical manual, like the Handbook for Marine Geotechnical Engineering, Chapter 7.

    Get the handbook and read it, more than you will ever need to know on mooring design and equipment

    Edit to add: Just looked at your linked document...that's the Navy Salvage Manual...just a condensed version of the Mooring Design handbook and the NCEL Marine Geotechnical Engineering handbook.
     
  4. VaurienH
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    VaurienH New Member


  5. floating
    Joined: Jun 2009
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    floating Junior Member

    jehardiman and VaurienH - Thanks for these useful references. They are just what I was looking for. I can see anchoring is a topic you can get embedded in (bad pun).
     
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