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Thread: What Chain?

  1. #21
    Join Date
    Jan 2004
    Posts
    2,068

    Default

    If weight is a major factor why not go for one of the modern unballasted designs like the http://www.bluewatersupplies.com/oc.htm or the http://www.bluemarinestore.com/raya-anchor.html I've no experience of the Sword but have slept soundly on my Raya for the last three seasons. For equivalent holding power they are about half the weight of a modern ballasted anchor e.g. the Raya 600 has the same fluke area, 60sq.cm, as the Spade 60 but weighs 4.75kg to the Spade's 10kg.
    Last edited by machurley22; 24-02-12 at 14:34.

  2. #22
    jdc is offline Registered User
    Location : Falmouth
    Join Date
    Dec 2007
    Posts
    654

    Default long and thin or short and fat?

    I do have a catenary calculaor, and have done the calcs for mixed chain-rope rodes supposing:

    1. you have a fixed total weight, so weight per metre x number of meters of chain = constant, and

    2. you want to let out the minimum toal length of rode (rope + chain) to just keep the pull at the anchor horizontal.

    Under these two constaints then despite variations in depth and wind strength you need less total scope when you have the shorter length of heavier chain. I have posted a graph of it on here before.

    However, and it's a big however, 1. is dubious because one should really optimise for total weight including anchor, and 2. is challeged by many experienced people who point out that (a) keeping the pull at the anchor horizontal is probably impossible anyway in extreme conditions, so unnecessary in normal conditions and (b) minimising the total scope is rather an arbitrary goal.

    (And if you do try to than take account of anchor weight, or calculate by how much the holding power will fall off with 'lift' of chain at the anchor, sometimes known as 'angulation', I must warn you that you will have transgressed many taboos).

    Nonetheless most kedge arrangements tend to use rather heavier chain than would be normal for the anchor's size (my Fortress was supplied with a short length of 12mm chain for instance). It strikes me that the OP's arrangement is really a kedge, and so normal practice for a kedge is appropriate.

  3. #23
    Join Date
    Oct 2001
    Posts
    145

    Default Safety Issue: an anchor is not just for lunch.

    Even if one only intends to use an anchor for lunch stops, I believe that there is still a real need to be able to deploy an effective anchor and chain or warp combination at short notice. This can make the difference between inconvenience and disaster. What if, on the return to a home port in rough conditions, the engine fails or you pick up a piece of net or rope on the prop or rudder? Anchored securely, you can attempt to fix the problem or await a tow. The alternative may be to be blown or swept onto the rock armour of a breakwater within minutes. I have personal experience of this in a fishing boat, fortunately the anchor held us off the broken base of a harbour pier. For this reason, I firmly believe that nobody should go to sea without an appropriate anchoring set-up, including the ability to recover the anchor in strong winds.

  4. #24
    Join Date
    Jun 2001
    Posts
    1,092

    Default

    I have slightly smaller boat than you and use Fortress FX16 with 15m of 8mm chain and 40m of 14mm anchor plait. I've over nighted on the anchore in strong tides (Chichester Harbour) with no problems. The Fortress is great, sets well and is light enough to handle easily back into the anchor locker. Don't under estimate the weight of chain it seems to weigh loads when hanging under the boat, despite the light weight go the Fortress.
    Beneteau First 31.7 owners Site http://www.beneteaufirst317.webs.com/

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