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Thread: Masts Leaning Backward

  1. #1
    Midshipman
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    Default Masts Leaning Backward

    Why are the masts on smaller vessels like brigs, schooners, etc. sometimes built to lean slightly backward?

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    2nd Lieutenant
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    The lean of the mast is called rake, as in, "the mast is raked aft".

    Sailing relies on a balance between the center of effort in the sails and the center of lateral resistance in the hull. If there's an imbalance, you can feel it in the rudder or the behavior of the boat, and trim or even reef (shorten) the sails to find the balance.

    As the wind picks up, the center of effort (COE) moves aft, and the boat wants to turn toward the wind. By reefing a fore and aft sail on a mast that's raked aft, you not only shorten the amount of sail area, but move the COE forward, which helps the boat resist turning toward the wind too aggressively.

    There's more to it, but I wanted to limit my response to a paragraph to keep it from sounding like, "blah, blah, blah!"
    Last edited by Dobbs; 05-04-2019 at 20:13.

  3. #3
    Admiral of the Blue.
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    Just been reading a book, where the ships Master not only has the masts raked differently to get better speed but has a longer mast shaved down in thickness but left higher than the present one also to enhance sailing qualities.

    How feasible is that Dobbs? What difference would it make to the ships performance?
    Rob.
    The Business of the commander-in-chief is first to bring an enemy fleet to battle on the most advantageous terms to himself, (I mean that of laying his ships close on board the enemy, as expeditiously as possible); and secondly to continue them there until the business is decided.

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    Quote Originally Posted by Bligh View Post
    Just been reading a book, where the ships Master not only has the masts raked differently to get better speed but has a longer mast shaved down in thickness but left higher than the present one also to enhance sailing qualities.

    How feasible is that Dobbs? What difference would it make to the ships performance?
    Rob.
    Rob, it's entirely feasible and can make a world of difference.

    Sailing is the balancing of 2 forces; the wind and water. The sails have a "center of effort", and the hull has a "center of lateral resistance". If these are balanced, the boat goes straight.

    Picture a rooster windvane. The center of lateral resistance(CLR) is the pivot point. The tail is the center of effort (COE). Because the tail is so big, the COE is too far aft, and the rooster always points into the wind. If it were a ship, it would be stuck in the red arc.

    To sail the rooster efficiently, either the head would need to be enlarged, or the tail shrunk to make the pressure even on both sides of the balance point (CLR).

    The rudder can compensate for some of the lack of balance, but the more the rudder is needed, the slower the boat goes.

    Moving/reshaping the masts and sails is an extreme measure (the designer should have put everything where it belongs), but entirely do-able.

    This sort of thing is one of the things Suzanne and I do to modern boats. In fact, our boat, Grace was so out of tune when we got her that she was slow and had a hard time tacking. We shortened the forestay, which decreased the rake and shifted the top of the mast forward. This moved the sail plan forward, and balanced the COE with the CLR. It turns out that one of her previous owners increased the rake (reason unknown) from what the designer had envisioned and we just put it back. We saw a significant improvement in the boat.

    I hope this is helpful.

  5. #5
    Admiral of the Blue.
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    Thank you for taking the time to explain this to a complete lubber Dobbs. It has clarified in one or two paragraphs something that I was struggling to understand from my books even before the curved of altering the masts.
    Full marks for using the rooster vane as an exemplar. It is something I can understand totally as I have made a few over the years for friends. Must get one done for myself one of these days. Problem is Sea-witch or HMS Victory?
    Rob.
    The Business of the commander-in-chief is first to bring an enemy fleet to battle on the most advantageous terms to himself, (I mean that of laying his ships close on board the enemy, as expeditiously as possible); and secondly to continue them there until the business is decided.

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    Thanks for the knowledge bomb, Dobbs. That's so interesting. Makes a lot of sense indeed.

  7. #7
    Admiral of the Blue.
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    Welcome to the Anchorage on behalf of the shipmates anchored here.
    It was indeed a very interesting little explanation by Dobbs. You will find a lot of very knowledgeable fellows here.
    Do drop into the Wardroom for a chinwag and a few virtual pints of your favourite brew.
    Rob.
    The Business of the commander-in-chief is first to bring an enemy fleet to battle on the most advantageous terms to himself, (I mean that of laying his ships close on board the enemy, as expeditiously as possible); and secondly to continue them there until the business is decided.

  8. #8
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    Interesting, I was aware of the terms but thanks for the explanation

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    Quote Originally Posted by Capn Duff View Post
    Interesting, I was aware of the terms but thanks for the explanation
    My pleasure, Chris, and thanks Mark. I love the term "knowledge bomb".

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