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Re: Steve's Mayfly 14 Build - Mast Rake

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  • prairiedog2332
    Yes - it is as Anders mentions. It is explained on pages 142 (Sail area math) and pages 66-68. And it requires the mast to be a foot taller as shown on the
    Message 1 of 6 , Jul 29, 2013
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      Yes - it is as Anders mentions. It is explained on pages 142 (Sail area
      math) and pages 66-68. And it requires the mast to be a foot taller as
      shown on the drawing opposite page 28. 10' tall rather than 9'.

      Jim moved the halyard attachment point higher up the yard than
      considered traditional to allow for some halyard stretch. (40% rather
      than about 33%) So that shifted the centroid of the sail forward so to
      get it back where it belonged the easiest way is to rake the mast a bit.


      You will also note he mentions that getting the balance correct to
      insure just a tad of weather helm is affected by several factors. The
      cut of the sail, halyard location and stretch, the underwater foils and
      even where you and crew are sitting. So some final tweaking may an idea
      once you get used to the boat. The easiest way is to adjust the mast
      rake and it is important to have the mast partner adjustable. Have some
      extra length on the bolts to allow for shims for example. (Page 45). And
      make the mast a bit taller than called for. On longer hulls adding a
      mizzen is another option.


      Light, shallow draft boats with with narrow foils are much more
      sensitive to getting the balance correct than deeper hulls with longer
      keels.


      Nels

      Nels


      --- In Michalak@yahoogroups.com, Anders Bjorklund wrote:
      >
      > My guess is it's for one of two reasons. Either the sailplan needed to
      be
      > shifted aft for better helm balance, or (more likely) the halyard
      needed to
      > be attached higher on the yard to improve the set of the balanced lug
      sail.
      > The increase in mast rake might require a slightly taller mast, so you
      > should also check the plans for that. If you send an email to Jim, he
      will
      > probably eventually get back to you, and clear up any lingering
      confusion.
      >
      > Anders
      >
      >
      > On Sun, Jul 28, 2013 at 9:49 PM, scast101 scast101@... wrote:
      >
      > > **
      > >
      > >
      > > JM's plans show a revised mast rake - it angles aft more than the
      > > original. No notes that I can find in the book however. I'm assuming
      that
      > > the revised angle is what I need to build. Can any one confirm? Any
      one
      > > know the reason for the revisions?
      > >
      > > Thanks!
      > >
      > > Steve
      > >
      > >
      > >
      >
      >
      > [Non-text portions of this message have been removed]
      >



      [Non-text portions of this message have been removed]
    • Anders Bjorklund
      Nice job digging out page numbers from Jim s book Nels. I m not sure I m with you on your comment below though. It seems like a stretchy halyard, if left
      Message 2 of 6 , Jul 29, 2013
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        Nice job digging out page numbers from Jim's book Nels. I'm not sure I'm
        with you on your comment below though. It seems like a stretchy halyard, if
        left unchecked by a parrel or something similar, would allow the centroid
        to pivot get back "where it belongs", without adding rake to the mast. I do
        like the revised mast rake setup though. It looks like it would reduce sail
        twist, and produce a better balanced sail.

        Even on an inexpensive boat, I think paying for low stretch line for a
        halyard is extra money well spent. I also believe in yard parrels, or
        rigging the halyard with a loop around the mast, so the yard does not pivot
        aft when the sail is reefed (or the cheap halyard stretches).

        Cheers,
        Anders


        On Mon, Jul 29, 2013 at 8:28 AM, prairiedog2332 <nelsarv@...> wrote:

        > Jim moved the halyard attachment point higher up the yard than
        > considered traditional to allow for some halyard stretch. (40% rather
        > than about 33%) So that shifted the centroid of the sail forward so to
        > get it back where it belonged the easiest way is to rake the mast a bit.
        >


        [Non-text portions of this message have been removed]
      • prairiedog2332
        Anders, I realized my error when I was out this morning and see you have already noted it:-) In the old days the halyard was attached about 33% up from the
        Message 3 of 6 , Jul 29, 2013
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          Anders,

          I realized my error when I was out this morning and see you have already
          noted it:-)

          In the old days the halyard was attached about 33% up from the lower end
          of the yard and due to halyard stretch, in real-life use back then -
          was about the same as attaching it 40% up with the newer non-stretch
          lines we have now. And according to Jim that is why he changed the
          attachment point.

          A lot of sailors are doing it a bit differently now based on the
          re-discovery of another option. This includes Mik Storer and John
          Welsford and John Boy also from this group. The halyard is attached to
          the very lower end of the yard then goes up and back behind the mast and
          through a block or loop of line that is attached to yard at the 40%
          location and then up through the block at the top of the mast and back
          down to be in easy reach of the helm.


          This photo of Scamp gives a fairly good illustration. Seems there is
          another block at the base of this mast running to a cleat within reach
          of the skipper.

          http://www.duckworksbbs.com/plans/jw/scamp/index.htm
          <http://www.duckworksbbs.com/plans/jw/scamp/index.htm>

          With this option there is no need for a parrel. And yes this also seems
          to reduce sail twist and yes getting good line is worth the cost. This
          is considered to be about the best.

          http://www.duckworksbbs.com/line/krypton/d/index.htm
          <http://www.duckworksbbs.com/line/krypton/d/index.htm>

          Nels

          --- In Michalak@yahoogroups.com, Anders Bjorklund wrote:
          >
          > Nice job digging out page numbers from Jim's book Nels. I'm not sure
          I'm
          > with you on your comment below though. It seems like a stretchy
          halyard, if
          > left unchecked by a parrel or something similar, would allow the
          centroid
          > to pivot get back "where it belongs", without adding rake to the mast.
          I do
          > like the revised mast rake setup though. It looks like it would reduce
          sail
          > twist, and produce a better balanced sail.
          >
          > Even on an inexpensive boat, I think paying for low stretch line for a
          > halyard is extra money well spent. I also believe in yard parrels, or
          > rigging the halyard with a loop around the mast, so the yard does not
          pivot
          > aft when the sail is reefed (or the cheap halyard stretches).
          >
          > Cheers,
          > Anders




          [Non-text portions of this message have been removed]
        • Anders Bjorklund
          Yes, a lot of sailors have picked up on the Dixon Kemp method of rigging their lug halyard that you mentioned below:
          Message 4 of 6 , Jul 29, 2013
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            Yes, a lot of sailors have picked up on the Dixon Kemp method of rigging
            their lug halyard that you mentioned below:

            http://www.duckworksbbs.com/plans/jw/scamp/index.htm

            It works fine when sailing with a full sail, and never causes trouble while
            hoisting or striking the rig. But that photo is a good illustration of what
            I don't like about it when a reef is tied in. Notice how the rig has
            pivoted aft from its normal location, with the boom end drooping into the
            cockpit. Now imagine what is going to happen to the rig when he bears off
            the wind. The yard will be free to saw back and forth against the mast,
            possibly inducing death rolls that can capsize the boat. Even Josh Colvin,
            SCAMP's developer, said he is experimenting with other methods, because the
            rig shown in the photo leaves the yard "out of control" (his phrase) with a
            reefed sail.

            A beaded parrel on the halyard usually works well, and other methods of
            just rigging the halyard with a loop around the mast are effective in
            controlling the position of a reefed lugsail.

            Cheers,
            Anders


            On Mon, Jul 29, 2013 at 7:16 PM, prairiedog2332 <nelsarv@...> wrote:

            > I realized my error when I was out this morning and see you have already
            > noted it:-)
            >
            > In the old days the halyard was attached about 33% up from the lower end
            > of the yard and due to halyard stretch, in real-life use back then -
            > was about the same as attaching it 40% up with the newer non-stretch
            > lines we have now. And according to Jim that is why he changed the
            > attachment point.
            >
            > A lot of sailors are doing it a bit differently now based on the
            > re-discovery of another option. This includes Mik Storer and John
            > Welsford and John Boy also from this group. The halyard is attached to
            > the very lower end of the yard then goes up and back behind the mast and
            > through a block or loop of line that is attached to yard at the 40%
            > location and then up through the block at the top of the mast and back
            > down to be in easy reach of the helm.
            >
            > This photo of Scamp gives a fairly good illustration. Seems there is
            > another block at the base of this mast running to a cleat within reach
            > of the skipper.
            >
            > http://www.duckworksbbs.com/plans/jw/scamp/index.htm
            > <http://www.duckworksbbs.com/plans/jw/scamp/index.htm>
            >
            > With this option there is no need for a parrel. And yes this also seems
            > to reduce sail twist and yes getting good line is worth the cost. This
            > is considered to be about the best.
            >
            > http://www.duckworksbbs.com/line/krypton/d/index.htm
            > <http://www.duckworksbbs.com/line/krypton/d/index.htm>
            >
            > Nels
            >


            [Non-text portions of this message have been removed]
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