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Re: Single junk sails on boats over 32'

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  • edward_stoneuk
    Thanks Victor. I think that 700 sq ft would suit me. Do you think that a single mast rig of that size would be lighter than a twin masted rig? In heavy
    Message 1 of 15 , Mar 1, 2004
      Thanks Victor.
      I think that 700 sq ft would suit me. Do you think that a single
      mast rig of that size would be lighter than a twin masted rig? In
      heavy weather I can see that the last bit of reefing would be more
      difficult with a single sail. That said small single masted rigs
      sail far away and I guess that balance and handling is a question of
      scale or am I wrong?
      Regards,
      Ted
    • Victor Winterthun
      Ted Volumes and veights will change with the 3 power of the change in scale, so I belive that two masts will be lighter. Victor ... From: edward_stoneuk
      Message 2 of 15 , Mar 1, 2004
        Ted
        Volumes and veights will change with the 3 power of the change in scale, so I belive that two masts will be lighter.

        Victor

        ----- Original Message -----
        From: "edward_stoneuk" <tedstone@...>
        To: <junkrig@yahoogroups.com>
        Sent: Monday, March 01, 2004 9:23 PM
        Subject: [junkrig] Re: Single junk sails on boats over 32'


        > Thanks Victor.
        > I think that 700 sq ft would suit me. Do you think that a single
        > mast rig of that size would be lighter than a twin masted rig? In
        > heavy weather I can see that the last bit of reefing would be more
        > difficult with a single sail. That said small single masted rigs
        > sail far away and I guess that balance and handling is a question of
        > scale or am I wrong?
        > Regards,
        > Ted
      • sae140
        ... Hi Ted Just sticking my oar in here ... I don t know the source, but I ve always understood that 100 sq ft per ton is considered optimum for junk sails.
        Message 3 of 15 , Mar 2, 2004
          --- In junkrig@yahoogroups.com, "edward_stoneuk" <tedstone@g...>
          wrote:
          > Thanks Victor.
          > I think that 700 sq ft would suit me.


          Hi Ted

          Just sticking my oar in here ...

          I don't know the source, but I've always understood that 100 sq ft
          per ton is considered optimum for junk sails.
          This figure is supported by the Wylo 35 (a broadly similar hull form
          to the Swain) at 6.9 tons flying 714 sq ft on 2 sticks, so I would
          have thought that the Swain 36, being almost a ton heavier, really
          ought to fly 800 sq ft minimum (Victor's upper figure).

          Also, I understand that some folks increase the sail area well above
          100 sq ft per ton to give extra sail area in light airs - i.e. with
          one reef being the normal working sail configuration - which would
          suggest even more than 800 sq ft..

          Colin
        • Victor Winterthun
          Hi The usual way to compare sailarea is as follows: SA/volume^2/3 = max 13 (Motorsailer) If depl. is 18000lbs. will it give 558 sq.ft. 19 Genrous area
          Message 4 of 15 , Mar 2, 2004
            Hi
            The usual way to compare sailarea is as follows:
            SA/volume^2/3 = max 13 (Motorsailer) If depl. is 18000lbs. will it give 558 sq.ft.
            19 Genrous area " " " " 815 " "
            I have to admit that my own boat have 21, but I have to reef at 7m/s.

            The weight of 1 cu. ft of sea water is 64lbs.
            18000lbs/64 = 281.25 cu.ft. = Volume of displasement.
            SA/281.25^0.667 = 16 ): SA = 687 sq.ft.

            Victor

            ----- Original Message -----
            From: "sae140" <colinpowell@...>
            To: <junkrig@yahoogroups.com>
            Sent: Tuesday, March 02, 2004 9:30 PM
            Subject: [junkrig] Re: Single junk sails on boats over 32'


            > --- In junkrig@yahoogroups.com, "edward_stoneuk" <tedstone@g...>
            > wrote:
            > > Thanks Victor.
            > > I think that 700 sq ft would suit me.
            >
            >
            > Hi Ted
            >
            > Just sticking my oar in here ...
            >
            > I don't know the source, but I've always understood that 100 sq ft
            > per ton is considered optimum for junk sails.
            > This figure is supported by the Wylo 35 (a broadly similar hull form
            > to the Swain) at 6.9 tons flying 714 sq ft on 2 sticks, so I would
            > have thought that the Swain 36, being almost a ton heavier, really
            > ought to fly 800 sq ft minimum (Victor's upper figure).
            >
            > Also, I understand that some folks increase the sail area well above
            > 100 sq ft per ton to give extra sail area in light airs - i.e. with
            > one reef being the normal working sail configuration - which would
            > suggest even more than 800 sq ft..
            >
            > Colin
            >
            >
            >
            >
            >
            >
            >
            > The junkrig "Files" section is at: http://groups.yahoo.com/group/junkrig/files/
            > The overflow "Files" section is at: http://groups.yahoo.com/group/junkrig2/files/
            > The "Photos" section is at: http://photos.groups.yahoo.com/group/junkrig/lst
            > The "Links" section is at: http://groups.yahoo.com/group/junkrig/links
            >
            >
            >
            >
            > --------------------------------------------------------------------------------
            > Yahoo! Groups Links
            >
            > a.. To visit your group on the web, go to:
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            >
          • knoeter2000
            And what is the weight of such a big mast and sail doing just at the bow where you do´nt want to have much. Might be difficult to get a good trim or?
            Message 5 of 15 , Mar 3, 2004
              And what is the weight of such a big mast and sail doing just at the
              bow where you do´nt want to have much. Might be difficult to
              get a good trim or?
            • Don Taylor
              ... give 558 sq.ft. ... 815 ... 7m/s. ... This is the Sail Area to Displacement calculation. There is a handy little web-based
              Message 6 of 15 , Mar 3, 2004
                --- In junkrig@yahoogroups.com, "Victor Winterthun"
                <victor.winterthun@c...> wrote:
                > Hi
                > The usual way to compare sailarea is as follows:
                > SA/volume^2/3 = max 13 (Motorsailer) If depl. is 18000lbs. will it
                give 558 sq.ft.
                > 19 Genrous area "
                " " " 815 " "
                > I have to admit that my own boat have 21, but I have to reef at
                7m/s.
                >
                > The weight of 1 cu. ft of sea water is 64lbs.
                > 18000lbs/64 = 281.25 cu.ft. = Volume of displasement.
                > SA/281.25^0.667 = 16 ): SA = 687 sq.ft.
                >
                > Victor


                This is the "Sail Area to Displacement" calculation. There is a handy
                little web-based calculator for this and other standard NA
                calculations at:

                http://www.sailingusa.info/cal__sad_ratio.htm

                Don.
              • sae140
                ... it give 558 sq.ft. ... area 815 ... 7m/s. ... Hi Victor the trouble wth formulas containing
                Message 7 of 15 , Mar 4, 2004
                  --- In junkrig@yahoogroups.com, "Victor Winterthun"
                  <victor.winterthun@c...> wrote:
                  > Hi
                  > The usual way to compare sailarea is as follows:
                  > SA/volume^2/3 = max 13 (Motorsailer) If depl. is 18000lbs. will
                  it give 558 sq.ft.
                  > 19 Genrous
                  area " " " " 815 " "
                  > I have to admit that my own boat have 21, but I have to reef at
                  7m/s.
                  >
                  > The weight of 1 cu. ft of sea water is 64lbs.
                  > 18000lbs/64 = 281.25 cu.ft. = Volume of displasement.
                  > SA/281.25^0.667 = 16 ): SA = 687 sq.ft.
                  >
                  > Victor


                  Hi Victor

                  the trouble wth formulas containing two-thirds powers is that they
                  give me a headache (!) and I have to resort to using a calculator, so
                  much prefer to use 100 sq.ft. per ton as a rough-and-ready
                  yardstick.

                  Re: formulas - I actually prefer the formula that Tom Colvin uses,
                  i.e. Sail Area (in sq.ft.) divided by displacement (in 2240 lb long
                  tons) to the two-thirds power. Using this formulae, his Gazelle -
                  which at 18000 lbs is the same displacement as Ted Stone's hull - has
                  a SA/displacement figure of 212 when flying 854 sq.ft of sail (not
                  including jib). That's 107 sq.ft per ton using my yardstick.

                  Using this formulae, the Wylo 35 at 15400 lbs and 714 sq.ft.
                  mentioned earlier gives an SA/Disp figure of 198 [or 104 sq.ft per
                  ton], and Badger at 10,400 lbs and 600 sq.ft. gives a SA/Disp figure
                  of 216 (or 129 sq.ft per ton).

                  Clearly the lighter the boat, the more my yardstick is in error, as
                  can be seen with Pilmer (Kingfisher 20) at 2700 lbs and 227 sq.ft.,
                  giving a SA/Disp figure of 200, but a whacking 189 using this
                  yardstick.

                  So it appears that the 100 sq.ft per ton yardstick only has validity
                  for boats in the 6-9 ton class. (which just happens to be my area of
                  interest !)


                  However, I'd still respectfully suggest that Ted Stone's boat should
                  be flying at least 800 sq.ft. - the reason being that - if I
                  understand the dilemma accurately - it is not just a question of sail
                  area (which can always be adjusted later), but whether to fly two
                  masts or one. Retro-fitting from one mast to two could be an
                  expensive option, especially if the hull is at an advanced stage of
                  fitting-out.

                  Just my 2-penn'orth on this one. Going back to sleep now.

                  With best wishes

                  Colin
                • Victor Winterthun
                  Thank you Don. I will bookmark that address. Victor
                  Message 8 of 15 , Mar 4, 2004
                    Thank you Don.
                    I will bookmark that address.

                    Victor

                    > > The weight of 1 cu. ft of sea water is 64lbs.
                    > > 18000lbs/64 = 281.25 cu.ft. = Volume of displasement.
                    > > SA/281.25^0.667 = 16 ): SA = 687 sq.ft.
                    > >
                    > > Victor
                    >
                    >
                    > This is the "Sail Area to Displacement" calculation. There is a handy
                    > little web-based calculator for this and other standard NA
                    > calculations at:
                    >
                    > http://www.sailingusa.info/cal__sad_ratio.htm
                    >
                    > Don.
                  • Don Taylor
                    ... give 558 sq.ft. ... 815 ... I think that Victor s plan makes a lot of sense if you can find a way to fly that much sail area (SA/D =
                    Message 9 of 15 , Mar 4, 2004
                      --- In junkrig@yahoogroups.com, "Victor Winterthun"
                      <victor.winterthun@c...> wrote:
                      > Hi
                      > The usual way to compare sailarea is as follows:
                      > SA/volume^2/3 = max 13 (Motorsailer) If depl. is 18000lbs. will it
                      give 558 sq.ft.
                      > 19 Genrous area "
                      " " " 815 " "
                      > I have to admit that my own boat have 21, but I have to reef at 7m/s.

                      I think that Victor's plan makes a lot of sense if you can find a way
                      to fly that much sail area (SA/D = 21) because on a JR you cannot add
                      much in the way of light air sails. Design the rig with a large sail
                      area, but plan the first reef configuration as if it were the working
                      sail plan. This means that you should plan the CoE of the sails based
                      upon the first reef.

                      You can see that some traditional Chinese sails do this. The bottom
                      panels are often shown reefed up except when reaching or running in
                      light airs. Then the bottom panel is dropped and it almost touches
                      the water - you would probably have to reef it up to gybe or come
                      about. The bottom panel is controlled by a separate tag line rather
                      than being part of the main running rigging. The lowest sheetlet
                      would be attached to the first batten above the boom.

                      Don.
                    • Ben Tucker
                      Hi all A similar way to increase the light air SA is the watersail used on gaffers. This is any old sail, we use an old headsail with the clew pulled out to
                      Message 10 of 15 , Mar 4, 2004
                        Hi all

                        A similar way to increase the light air SA is the watersail used on
                        gaffers. This is any old sail, we use an old headsail with the clew
                        pulled out to the end of the boom, the head is lashed around the mast
                        and a light sheet is taken from the tack.The luff is hanked onto the
                        main sail lashings. It droops all over the show and scoops up all the
                        wind whistling under the boom.

                        It Gets used mostley for reaching and running but would give an end
                        plate effect if used for windward work. Sheeting is not at all
                        critical.

                        Big problem is visibility, A custom WS would have a window. and be
                        made from light Nylon or something with a track along the boom.

                        This sail would suit a low aspect junk well because of the long boom.
                        It is safer than dropping the boom height because it is loose footed.

                        The Best thing about it is the funny looks on the Bermudian boat
                        owners faces as we sail past.

                        Cheers

                        Ben
                      • Ben Tucker
                        Sorry for the apparently unrelated topic since my last post has been moderated and the topic has moved on abit i d should point out that I was Inspired by
                        Message 11 of 15 , Mar 5, 2004
                          Sorry for the apparently unrelated topic

                          since my last post has been moderated and the topic has moved on abit
                          i'd should point out that I was Inspired by don's comments below
                          about the extra bottom panel. Also Wonder if a watersail could reduce
                          a usefull vortex generated off the boom end?

                          Some pix of a watersail on an open 60 and an old gaffer at

                          http://perso.wanadoo.fr/orion.charter/images/album/145-Boom%20and%
                          20watersail%20at%20sunset.jpg

                          http://www.torresen.com/sailing/content_archives/000402.php

                          cheers

                          ben

                          > You can see that some traditional Chinese sails do this. The bottom
                          > panels are often shown reefed up except when reaching or running in
                          > light airs. Then the bottom panel is dropped and it almost touches
                          > the water - you would probably have to reef it up to gybe or come
                          > about. The bottom panel is controlled by a separate tag line rather
                          > than being part of the main running rigging. The lowest sheetlet
                          > would be attached to the first batten above the boom.
                          >
                          > Don.
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