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Re: JUNK RIG ADVISE

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  • sa.figueiredo
    Cher Bertrand Once again merci bien . Now I have the complete picture. What is your opinion about the wishbones having the same size of the battens? Do you
    Message 1 of 27 , Sep 1 10:41 AM
      Cher Bertrand

      Once again "merci bien". Now I have the complete picture. What is your
      opinion about the wishbones having the same size of the battens?
      Do you beleive that this will improve the sail performance? Luis.
    • bmhfercot
      Dear Luis I have not enough experiences to tell you what is the best balance between the length of the wishbones and of the battens. On the Tiki46 sail plan
      Message 2 of 27 , Sep 19 7:27 AM
        Dear Luis

        I have not enough experiences to tell you what is the best balance
        between the length of the wishbones and of the battens.

        On the Tiki46 sail plan (Swing wing rig design) the wishbones have the
        2/3 of the total length and the battens 1/3. As the bottom of the sail
        is 6m length, it could be easier and lighter to make them with a 50/50
        proportion : 3 m length for the wishbone and batten, but I don't know
        if the efficiency is better. Only the experiments can reply.
        If for a plane it's easy to find the best efficient profile at
        cruising speed, for a sail boat it's impossible as the relative wind
        is changing from 0 kts to gale force.

        Unhappily for us, on this forum people who have experimented this type
        of junk rig are few. The only method is to make experiments.

        Tell me if you have some ideas.

        Amistad

        Bertrand


        --- In junkrig@yahoogroups.com, "sa.figueiredo" <sa.figueiredo@...> wrote:
        >
        > Cher Bertrand
        >
        > Once again "merci bien". Now I have the complete picture. What is your
        > opinion about the wishbones having the same size of the battens?
        > Do you beleive that this will improve the sail performance? Luis.
        >
      • Slieve
        Hi Luis/ Bertrand All rigs are a compromise and at the moment it would appear that the best aerodynamic/ most mechanically practical compromise for a soft
        Message 3 of 27 , Sep 19 9:13 AM
          Hi Luis/ Bertrand
          All rigs are a compromise and at the moment it would appear that the best aerodynamic/ most mechanically practical compromise for a soft wingsail would be as drawn on page 7 of the Junk Rig Association newsletter number 47. This has a 50:50 wishbone to straight batten ratio, with a well rounded entry, and is based on the Benedek 6407E section. David Tyler used this section as his starting point and seems to be pleased with the results having sailed from the UK to Capetown, Panama and is now somewhere in the Pacific.
          The structure of the Swing-Wing, and Bertrand's wooden adaptation of it seems to be perfectly good. The problem is that the sharp leading edge and small flap tend to give a lower lift/ drag ratio than can be achieved with a section like the one mentioned above. The blunt leading edge should be reasonably tolerant to a varying wind direction.
          Regards,
          Slieve.

          ----- Original Message -----
          From: bmhfercot
          To: junkrig@yahoogroups.com
          Sent: Wednesday, September 19, 2007 3:27 PM
          Subject: [junkrig] Re: JUNK RIG ADVISE


          Dear Luis

          I have not enough experiences to tell you what is the best balance
          between the length of the wishbones and of the battens.

          On the Tiki46 sail plan (Swing wing rig design) the wishbones have the
          2/3 of the total length and the battens 1/3. As the bottom of the sail
          is 6m length, it could be easier and lighter to make them with a 50/50
          proportion : 3 m length for the wishbone and batten, but I don't know
          if the efficiency is better. Only the experiments can reply.
          If for a plane it's easy to find the best efficient profile at
          cruising speed, for a sail boat it's impossible as the relative wind
          is changing from 0 kts to gale force.

          Unhappily for us, on this forum people who have experimented this type
          of junk rig are few. The only method is to make experiments.

          Tell me if you have some ideas.

          Amistad

          Bertrand

          --- In junkrig@yahoogroups.com, "sa.figueiredo" <sa.figueiredo@...> wrote:
          >
          > Cher Bertrand
          >
          > Once again "merci bien". Now I have the complete picture. What is your
          > opinion about the wishbones having the same size of the battens?
          > Do you beleive that this will improve the sail performance? Luis.
          >






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        • sa.figueiredo
          Dear friends Bertrand and Slieve. Bertrand - You would like to know if I have ideas about proportions of the wishbone/batten lengths. Unfortunately no. I am a
          Message 4 of 27 , Sep 20 9:41 AM
            Dear friends Bertrand and Slieve.

            Bertrand - You would like to know if I have ideas about proportions
            of the wishbone/batten lengths. Unfortunately no. I am a retired
            economist and my technical/mats knowledge is very limited. I like to
            study and read, but some times what I read is above my
            comprehension. Tord Erikson, member of this group gave us an
            excellent site – www.mh-aerotools.de/airfoils/javafoil.htm - but due
            to my insufficient technical background I am not sure of my
            conclusions. However, the following is my opinion, not very
            authoritative as mentioned above.
            There is a proved classic opinion that a sail should have the maximum
            camber in its first third. This can be easily done with the wishbone,
            however in the theory of lift, the flow from the upper and lower
            surfaces must merge smoothly for good velocity, but to increase an up
            force lift it is necessary to have a positive incidence in the wing,
            and to increase even more this lift power (although this will
            prejudice speed) the airplanes have a hinged flap. This is called
            split flap. The NACA – National Advisory Committee for Aerodynamics
            made wind tunnel tests of airfoils with and without split flaps and
            the conclusion was that when the flap was deflected the maximum lift
            coefficient was almost doubled. This information was obtain in an
            article written by R.W.Prout = Consultant in helicopter aerodynamics.
            Thus, if the batten is 1/3 of the wishbone length, in my opinion we
            have something similar to the split flap of the airplane wing
            i.e.when this 1/3 of the sail is deflected there is a substantial
            increase in the lift power The question is – do this substantial
            increase of the lift power will prejudice speed as it happens in the
            airplanes? It seems that a more conservative approach of a 50/50
            wishbone/batten might have a smoother result. I believe that the
            correct answer can only be obtained in a wind tunnel or by
            experimenting both approaches but this is obviously unpractical.
            Slieve – can you give me a clue of what is Benedek 6407E section ?
            Bertrand – I just received from Tiller bookshop the book Pratical
            Junk Rig by Hasler/McLeod – a very interesting book although has
            nothing about swing wing rigs. One thing that confused me in the book
            was the positive stagger on a furled sail. To obtain this they
            suggest that slope of the battens (in our case wishbone/batten) has a
            critical effect on reefing. The question is: - Do this slope of the
            battens are necessary on the wing ring system ? The book also
            mentions that the "...for full virtues of the junk sail the mean
            panel width should not be greater than one-third of the batten
            length, preferably a quarter and one-fifth" What do you think about
            this, do this also applies to the wing ring sail.?
            Best regards to all – Luis
          • bmhfercot
            Hi Luis and Slieve Thank you Slieve, I study with attention the drawing you gave me at Southampton and which is on page 7 of the Junk Rig Association
            Message 5 of 27 , Sep 25 8:17 AM
              Hi Luis and Slieve

              Thank you Slieve, I study with attention the drawing you gave me at
              Southampton and which is on page 7 of the Junk Rig Association
              newsletter number 47.On the page 9 we can see a beautiful picture of
              Tystie. In fact as David made all the wishbones equal, the fore sail
              has not a 50/50 proportion, only at the top and it seems better on the
              back sail.
              On your drawing where is the Benedek 6407E profile? Is it the profile
              of the wishbone or is it the profile of the complete curve : wishbone
              + batten which is the Benedek 6407E?.
              If it's well the complete profile, can you give us the Benedek 6407E
              section data and can you tell us which is the NACA section of the
              wishbone? Thank you.
              The section of the wishbone seems to be very very thick : 23% of the
              wishbone length. So for a total length of 6m, the wishbone's length
              will be 3m and its thickness will be 69cm. It seems too much.
              As I have to delay the launch day or our Tiki46 to the Summer 2009 due
              to lack of time and money, this winter I'll try to make new wishbones
              for our Tiki30. according your and David ideas. But at first I have to
              find data for a good wishbone profile.

              Sorry Luis, but even with a dictionary, I can't understand what means
              "positive stagger" in your request :
              > One thing that confused me in the book
              > was the positive stagger on a furled sail. To obtain this they
              > suggest that slope of the battens (in our case wishbone/batten) has
              > a critical effect on reefing. The question is: - Do this slope of
              > the battens are necessary on the wing ring system"
              On PHA I adjust the slope of the bottom wishbones-battens with the
              lazy jack.
              Concerning the mean panel width, on the Tiki30 and 46 it is about 1/3
              of the length of the wishbones-battens.
              Sure, in the book "Pratical Junk Rig" by Hasler/McLeod there is no
              study about the Swing Wing rig, but you have a lot of information to
              calculate your masts, to draw the sail and to gear your rig.

              Best regards.

              Bertrand
            • sa.figueiredo
              Cher ami Bertrand It was also impossible for me to translate stagger into Portuguese. I thought that my dictionary was out of date. Now I feel a little more
              Message 6 of 27 , Sep 25 2:26 PM
                Cher ami Bertrand

                It was also impossible for me to translate "stagger" into Portuguese. I
                thought that my dictionary was out of date. Now I feel a little more
                comfortable. However it is quite easy to understand what is the
                meaning of stagger if you look in the page 29 fig. 2.6 and 2.7 of the
                Practical Junk Rig. It might happen that you have a different edition
                of the one that I have. So this is what the authors mention about -
                "Stagger is the amount by which the ends of the furled battens overlap
                each other" The authors also mention that it is VERY important to have
                positive stagger. My question was - is this also important in the swing
                wing rig, or really doesn't matter? Aurevoir – Luis
              • mitt@hiline.net
                ... laying or layering. Deborah Anne Dubois-Kohne Jackson de Oliveira
                Message 7 of 27 , Sep 25 2:58 PM
                  >Escalonar is the word used in Portuguese (Brazil & Portugal) as in brick
                  laying or layering.
                  Deborah Anne Dubois-Kohne Jackson de Oliveira


                  > Cher ami Bertrand
                  >
                  > It was also impossible for me to translate "stagger" into Portuguese. I
                  > thought that my dictionary was out of date. Now I feel a little more
                  > comfortable. However it is quite easy to understand what is the
                  > meaning of stagger if you look in the page 29 fig. 2.6 and 2.7 of the
                  > Practical Junk Rig. It might happen that you have a different edition
                  > of the one that I have. So this is what the authors mention about -
                  > "Stagger is the amount by which the ends of the furled battens overlap
                  > each other" The authors also mention that it is VERY important to have
                  > positive stagger. My question was - is this also important in the swing
                  > wing rig, or really doesn't matter? Aurevoir – Luis
                  >
                  >
                  >
                  >
                  > The junkrig "Files" section is at:
                  > http://groups.yahoo.com/group/junkrig/files/
                  > The junkrig2 overflow "Files" section is at:
                  > http://groups.yahoo.com/group/junkrig2/files/
                  > The "Photos" section is at: http://groups.yahoo.com/group/junkrig/photos
                  > The junkrig2 overflow "Photos" section is at:
                  > http://groups.yahoo.com/group/junkrig2/photos/
                  >
                  > Yahoo! Groups Links
                  >
                  >
                  >
                  >
                • De Clarke
                  say, who s been writing the Wikipedia page on Junk Rig? http://en.wikipedia.org/wiki/Junk_rig not bad! de
                  Message 8 of 27 , Sep 25 5:35 PM
                    say, who's been writing the Wikipedia page on Junk Rig?

                    http://en.wikipedia.org/wiki/Junk_rig

                    not bad!

                    de

                    ............................................................................
                    :De Clarke, Software Engineer UCO/Lick Observatory, UCSC:
                    :Mail: de@... | Your planet's immune system is trying to get rid :
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                  • leo foltz
                    when you go to history at the top of the wiki page, you find that all the work so far was done by Bruce Bradford. I m glad to see that a member of our group
                    Message 9 of 27 , Sep 26 12:54 AM
                      when you go to history at the top of the wiki page, you find that all
                      the work so far was done by Bruce Bradford. I'm glad to see that a
                      member of our group finally found the time to start that junk rig wiki
                      thing. hope others, you?, can join him. this would make the plenty of
                      information we have collected over the years much more easy to access.
                      Leo
                      > say, who's been writing the Wikipedia page on Junk Rig?
                    • sa.figueiredo
                      Obrigado Deborah - Escalonar reflects quite well the meaning of stagger. Thank you - Luis
                      Message 10 of 27 , Sep 26 6:16 AM
                        Obrigado Deborah - Escalonar reflects quite well the meaning of
                        stagger.
                        Thank you - Luis
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