Anchor Plans / Designs

Discussion in 'Boat Design' started by rugludallur, Apr 9, 2009.

  1. rugludallur
    Joined: Jan 2006
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    rugludallur Rugludallur

    I wonder if I'm the only person out here to look at an overpriced plow style anchor and figure, "Hell, I could build that from 316 stainless for 1/2 the cost".

    Since 316 stainless can be sourced for about $2 per kg I figure I could build a decent stainless anchor for my 33' cruiser for about $40 and a whole lot of polishing work.

    The only thing that concerns me is getting the correct shape and for some designs what amount of lead ballast to include inside the anchor.

    Anyone out there have drawings / plans / dimensions / CAD files for Bruce / CQR / Plow / Danforth / Fortress anchors that they are willing to share with the rest of us?

    Anyone here ever tried building their own anchors?

    Jarl Stefansson
    http://dallur.com
     
  2. Submarine Tom

    Submarine Tom Previous Member

    Jarl,

    Interesting idea but, to answer your question: No.

    I've always managed to find used (i.e. tested and proven) anchors for

    anywhere from 1/10 to 1/2 the cost of new and they've never failed me.

    Lead in an anchor. Can't say I've ever heard of that. Must be some big

    anchor you're considering.

    Good luck, Tom
     
  3. mark775

    mark775 Guest

    No need for lead. The shape is not as advanced as one might think. The side flukes serve to right the anchor, the bottom forms a tangent to the direction of pull to bury the thing in clay, sand, etc.. These styles work poorly in round rocks that just fit nicely between the bottom and sides, i.e., grapefruit sized rocks in a 15 kilo model. Most of the time, unless in ideal holding ground (clay), they aren't as good as one thinks and are actually just snagged on a rock, shale, coal seam, etc.. If in kelp, they cut loose and skip easily (kelp beds are notoriously bad for this type anchor). whereas something with a stock will snag and hold on until ripped out.
    The calling card is durability of the one piece types and low cost for the Chinese copies. They will not hold as well in sand as Danforths and such - they just don't have the surface area. The only reason for one with a joint ( I forget the name. Is it CQR? ) is so it seats nicely in a bow roller on a cruising sailboat. It is said that they reset easily but IMO, not much more easily.
    Within moments of dropping a shiny creation to the bottom with the most expensive stainless chain available, it will find an immovable, unbreakable shale ledge and make itself comfortable until the end of time. Good luck
     
  4. rugludallur
    Joined: Jan 2006
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    Location: Iceland

    rugludallur Rugludallur

    I thought I would add something about why someone would use lead in anchors and incidentally why it's inefficient to use concrete for a mooring.

    Here are some sample density ratios for common materials:

    Water: 1
    Concrete: 2
    Steel: 7.8
    Lead: 11.3

    So the net submerged density is:

    Concrete: 1
    Steel: 6.8
    Lead: 10.3

    So a lead ballasted anchor can provide up to 15% more submerged weight than a steel anchor of the same dry weight.

    It also shows that a concrete mooring will need to be 85% heavier than a steel mooring to provide the same effect while submerged.

    I have a Delta where the center section forms a triangular enclosure with a ballast and that got me thinking about these things.

    By placing the ballast low in the anchor it also increases the odds of the anchor setting correctly by providing roll stability.

    Jarl
    http://dallur.com
     
  5. mark775

    mark775 Guest

    rugludallur, good info but that's making an assumption that mass has much to do with this type of anchor's holding power. Check out Fortress Anchors. They really do work pretty well if you don't let it free-fall and tangle in it's own chain and you don't get it near anything hard.
     
  6. TeddyDiver
    Joined: Dec 2007
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    TeddyDiver Gollywobbler

    It's defineatly mass where anchors holding power comes from. It's just not the mass of the anchor, instead it's the mass of the ground where it buries or attach itself that counts :)
    Different type of anchors for different grounds that is..
     
  7. peter radclyffe
    Joined: Mar 2009
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    Location: europe

    peter radclyffe Senior Member

    GO FOR IT, WELD TWO OLD PLOW SHARES TOGETHER, A CROSS BAR & A SHANK, IT WILL WORK
     
  8. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    I have plans for a Northhill, (great, easy anchor to make) that I can scale and send you. Then you can make one for me too and I will buy it.
     
  9. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    Anchor Weight

    TRUE, but also don't waste anchor weight by making it easier, make it bigger.
    Example;
    What holds better, a 20 inch, 30 lb anchor, or a 30 inch, 30lb anchor.
    If it is the same design, the bigger one, that is why fortress aluminum anchors are powerhouses, because people get bigger ones for the same weight.

    Make a anchor stronger, big in the ground, easy to remove and then light enough so you actually retrieve it. It makes no use to put 100lb anchor in a 20 foot boat that you can't pull up.
     
  10. rugludallur
    Joined: Jan 2006
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    Location: Iceland

    rugludallur Rugludallur

    Hey mydauphin,

    I think the shipping part might be an issue, I live in Iceland so the shipping would probably be more expensive than buying an anchor (another reason why I would prefer to build my own).

    Can you send me the design to jarl@dallur.com, do you mind if I put the files on a public website so the rest of the people on the forum can access it?

    Here is a link I found with a 3d model of a CQR, the proportions look about right:
    http://www.boatdesign.net/gallery/data/3054/2178CQR.igs

    Jarl
    http://dallur.com
     
  11. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    The one which buries itself better in the ground :D
     

  12. Submarine Tom

    Submarine Tom Previous Member

    It depends on the type of ground and the type of anchor.
     
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