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Twin Leeboards

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  • prairiedog2332
    When reviewing Bolger s writings on leeboards, there are ways to improve performance with two, at the price of added complication. So here goes... With two
    Message 1 of 28 , Mar 27, 2013
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      When reviewing Bolger's writings on leeboards, there are ways to improve
      performance with two, at the price of added complication. So here
      goes...

      With two boards, they should be canted outwards so the board is more
      vertical when heeled and it gets the board further away from being
      interfered with by the turbulence coming off the hull. A hull with
      sides more parallel to the direction you are going also helps along with
      the forward curvature ahead of the board matching the upwards curvature
      of the bottom which also lessens turbulence - the old seas of peas idea.
      To be most effective the board should be in clear water away from this
      turbulence.

      Asymmetrical boards also improve performance when you have two. I think
      the flat side should be on the outside of the board and the convex side
      on the inner surface to improve lift - or is it the other way around?
      Also some toe-in helps but can easily be overdone which slows the boat.
      1 or 2 degrees at max.

      Of course Jim's designs have to use a symmetrical board with no toe-in
      to have equal pointing ability. The flare on his hulls helps get the
      board out further without a very wide bottom brace, but it can't be
      canted outwards either. Perhaps Hapscut actually gets a good compromise
      with more flare and a heavier brace to support the board?

      In heavier seas it is suggested by Bolger that a centreboard probably
      works more effectively as it is down further under the hull and in
      quieter water less affected by turbulence, and of course it can be
      raised somewhat to improve speed without resulting in lee helm as much.
      In larger hulls like his later Advanced Sharpies he went to inside
      bilge boards instead of leeboads for that reason. These have proven to
      be a potential source of internal rot and leakage if not built really
      stoutly with a lot of epoxy sealant. Also each board on a two leeboard
      design has to have the same area as single centreboard (about 4 % of
      your sail area) and if both left down when short-tacking in light airs
      can really affect forward progress especially in a light displacement
      hull that carries not much momentum to get you through stays. Another
      reason so sail more freely and avoid pinching too much. Stuck in irons
      with two boards down is sure way of bobbing up and down and going
      nowhere.

      Another reason for having a small reliable OB. I think Jim has done his
      homework and saved us a lot of complications and headaches:-)

      Nels





      [Non-text portions of this message have been removed]
    • jhargrovewright2@juno.com
      Nels, I understand the theory and agree that a asymmetrical leeboard canted to windward should help a sailboat.but is there any data to back that up, that you
      Message 2 of 28 , Mar 27, 2013
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        Nels, I understand the theory and agree that a asymmetrical leeboard canted to windward should help a sailboat.but is there any data to back that up, that you know of. The best pointing boat that I have sailed with was a beautifully built proa designed and built by a French engineer here in Texas. He had two carbon fiber professionally built dagger boards, one for each direction, deployed one at a time.... He had each daggerboard canted to windward some amount. A very beautiful and very fast boat. I have built one boat (Grok) with 2 asymmetrical leeboards. They were hollow and low aspect (elephant ear)although I did not choose to cant them because they were intended to work in several modes and I decided not to favor one mode.. JIB

        ---------- Original Message ----------
        From: "prairiedog2332" <nelsarv@...>
        To: Michalak@yahoogroups.com
        Subject: [Michalak] Twin Leeboards
        Date: Thu, 28 Mar 2013 00:10:36 -0000


        <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
        When reviewing Bolger's writings on leeboards, there are ways to improve
        performance with two, at the price of added complication. So here
        goes...

        With two boards, they should be canted outwards so the board is more
        vertical when heeled and it gets the board further away from being
        interfered with by the turbulence coming off the hull. A hull with
        sides more parallel to the direction you are going also helps along with
        the forward curvature ahead of the board matching the upwards curvature
        of the bottom which also lessens turbulence - the old seas of peas idea.
        To be most effective the board should be in clear water away from this
        turbulence.

        Asymmetrical boards also improve performance when you have two. I think
        the flat side should be on the outside of the board and the convex side
        on the inner surface to improve lift - or is it the other way around?
        Also some toe-in helps but can easily be overdone which slows the boat.
        1 or 2 degrees at max.

        Of course Jim's designs have to use a symmetrical board with no toe-in
        to have equal pointing ability. The flare on his hulls helps get the
        board out further without a very wide bottom brace, but it can't be
        canted outwards either. Perhaps Hapscut actually gets a good compromise
        with more flare and a heavier brace to support the board?

        In heavier seas it is suggested by Bolger that a centreboard probably
        works more effectively as it is down further under the hull and in
        quieter water less affected by turbulence, and of course it can be
        raised somewhat to improve speed without resulting in lee helm as much.
        In larger hulls like his later Advanced Sharpies he went to inside
        bilge boards instead of leeboads for that reason. These have proven to
        be a potential source of internal rot and leakage if not built really
        stoutly with a lot of epoxy sealant. Also each board on a two leeboard
        design has to have the same area as single centreboard (about 4 % of
        your sail area) and if both left down when short-tacking in light airs
        can really affect forward progress especially in a light displacement
        hull that carries not much momentum to get you through stays. Another
        reason so sail more freely and avoid pinching too much. Stuck in irons
        with two boards down is sure way of bobbing up and down and going
        nowhere.

        Another reason for having a small reliable OB. I think Jim has done his
        homework and saved us a lot of complications and headaches:-)

        Nels

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







        [Non-text portions of this message have been removed]
      • prairiedog2332
        JIB, I do know Bolger spent a lot of time and effort investigating these ideas so I think was able to share some meaningful data but it has been spread all
        Message 3 of 28 , Mar 27, 2013
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          JIB,
          I do know Bolger spent a lot of time and effort investigating these
          ideas so I think was able to share some meaningful data but it has been
          spread all over his writings and was not a high priority for me to
          understand. Many of his ideas written in the "Messing About In Boats
          Magazine " I no longer subscribe to. He did a lot of proa investigation
          as well as almost anything else you can imagine.

          Many of the refinements involved racing which is not my bag a all.
          Efficiency with little effort or complication is mine:-)

          In your work - the idea of sailing elephant ear leeboards in shallow
          water with the shallow bottom serving as an end-plate - is something I
          totally agree with. IF you have a shallow "skimming dish" draft on the
          hull. The next thing that may help is a sail rig that doesn't heel the
          hull much. Bolger considers the sprit rig a possible option? We are
          talking broad reaching mostly, sailing on the dew:-D

          Nels


          --- In Michalak@yahoogroups.com, "jhargrovewright2@..."
          <jhargrovewright2@...> wrote:
          >
          > Nels, I understand the theory and agree that a asymmetrical leeboard
          canted to windward should help a sailboat.but is there any data to back
          that up, that you know of. The best pointing boat that I have sailed
          with was a beautifully built proa designed and built by a French
          engineer here in Texas. He had two carbon fiber professionally built
          dagger boards, one for each direction, deployed one at a time.... He
          had each daggerboard canted to windward some amount. A very beautiful
          and very fast boat. I have built one boat (Grok) with 2 asymmetrical
          leeboards. They were hollow and low aspect (elephant ear)although I did
          not choose to cant them because they were intended to work in several
          modes and I decided not to favor one mode.. JIB
          >




          [Non-text portions of this message have been removed]
        • jhargrovewright2@juno.com
          Nels, One of my biggest thrills is planning a sailboat in shallow water. Grok was built for that with a 4 wide almost flat bottom. The interesting thing is
          Message 4 of 28 , Mar 27, 2013
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            Nels, One of my biggest thrills is planning a sailboat in shallow water. Grok was built for that with a 4' wide almost flat bottom. The interesting thing is that the boat lifts up on top and gets very stiff with no heal even in big wind. Strange. The amazing thing is that if you lose the wind and drop into displacement you slow down to a crawl....very slow because the water has to go around the boat but when the wind picks up the boat gets back on top without much effort. I just can not explain that ease to get back up. It would seem to me that it would take much more energy. I must build a Grok II with what I learned. There is a 10 mile stretch of Laguna Madre South of Corpus Christi Bay that is perfect for this kind of boat.. I know that water like the back of my hand...since childhood... O yeah, two years ago on the Texas 200, I planned my very light Laguna for several miles on a broad reach in 1 to 1.5 feet of water... probably averaged 12-14 mph for 30 min. or so... JIB

            ---------- Original Message ----------
            From: "prairiedog2332" <nelsarv@...>
            To: Michalak@yahoogroups.com
            Subject: [Michalak] Re: Twin Leeboards
            Date: Thu, 28 Mar 2013 02:49:41 -0000


            <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
            JIB,
            I do know Bolger spent a lot of time and effort investigating these
            ideas so I think was able to share some meaningful data but it has been
            spread all over his writings and was not a high priority for me to
            understand. Many of his ideas written in the "Messing About In Boats
            Magazine " I no longer subscribe to. He did a lot of proa investigation
            as well as almost anything else you can imagine.

            Many of the refinements involved racing which is not my bag a all.
            Efficiency with little effort or complication is mine:-)

            In your work - the idea of sailing elephant ear leeboards in shallow
            water with the shallow bottom serving as an end-plate - is something I
            totally agree with. IF you have a shallow "skimming dish" draft on the
            hull. The next thing that may help is a sail rig that doesn't heel the
            hull much. Bolger considers the sprit rig a possible option? We are
            talking broad reaching mostly, sailing on the dew:-D

            Nels

            --- In Michalak@yahoogroups.com, "jhargrovewright2@..."
            <jhargrovewright2@...> wrote:
            >
            > Nels, I understand the theory and agree that a asymmetrical leeboard
            canted to windward should help a sailboat.but is there any data to back
            that up, that you know of. The best pointing boat that I have sailed
            with was a beautifully built proa designed and built by a French
            engineer here in Texas. He had two carbon fiber professionally built
            dagger boards, one for each direction, deployed one at a time.... He
            had each daggerboard canted to windward some amount. A very beautiful
            and very fast boat. I have built one boat (Grok) with 2 asymmetrical
            leeboards. They were hollow and low aspect (elephant ear)although I did
            not choose to cant them because they were intended to work in several
            modes and I decided not to favor one mode.. JIB
            >

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







            [Non-text portions of this message have been removed]
          • jhargrovewright2@juno.com
            Planing is spelled with one n. My apologies. ... From: jhargrovewright2@juno.com To: Michalak@yahoogroups.com Subject: Re:
            Message 5 of 28 , Mar 27, 2013
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              Planing is spelled with one n. My apologies.

              ---------- Original Message ----------
              From: "jhargrovewright2@..." <jhargrovewright2@...>
              To: Michalak@yahoogroups.com
              Subject: Re: [Michalak] Re: Twin Leeboards
              Date: Thu, 28 Mar 2013 03:26:34 GMT


              <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
              Nels, One of my biggest thrills is planning a sailboat in shallow water. Grok was built for that with a 4' wide almost flat bottom. The interesting thing is that the boat lifts up on top and gets very stiff with no heal even in big wind. Strange. The amazing thing is that if you lose the wind and drop into displacement you slow down to a crawl....very slow because the water has to go around the boat but when the wind picks up the boat gets back on top without much effort. I just can not explain that ease to get back up. It would seem to me that it would take much more energy. I must build a Grok II with what I learned. There is a 10 mile stretch of Laguna Madre South of Corpus Christi Bay that is perfect for this kind of boat.. I know that water like the back of my hand...since childhood... O yeah, two years ago on the Texas 200, I planned my very light Laguna for several miles on a broad reach in 1 to 1.5 feet of water... probably averaged 12-14 mph for 30 min. or so... JIB

              ---------- Original Message ----------
              From: "prairiedog2332" <nelsarv@...>
              To: Michalak@yahoogroups.com
              Subject: [Michalak] Re: Twin Leeboards
              Date: Thu, 28 Mar 2013 02:49:41 -0000

              <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
              JIB,
              I do know Bolger spent a lot of time and effort investigating these
              ideas so I think was able to share some meaningful data but it has been
              spread all over his writings and was not a high priority for me to
              understand. Many of his ideas written in the "Messing About In Boats
              Magazine " I no longer subscribe to. He did a lot of proa investigation
              as well as almost anything else you can imagine.

              Many of the refinements involved racing which is not my bag a all.
              Efficiency with little effort or complication is mine:-)

              In your work - the idea of sailing elephant ear leeboards in shallow
              water with the shallow bottom serving as an end-plate - is something I
              totally agree with. IF you have a shallow "skimming dish" draft on the
              hull. The next thing that may help is a sail rig that doesn't heel the
              hull much. Bolger considers the sprit rig a possible option? We are
              talking broad reaching mostly, sailing on the dew:-D

              Nels

              --- In Michalak@yahoogroups.com, "jhargrovewright2@..."
              <jhargrovewright2@...> wrote:
              >
              > Nels, I understand the theory and agree that a asymmetrical leeboard
              canted to windward should help a sailboat.but is there any data to back
              that up, that you know of. The best pointing boat that I have sailed
              with was a beautifully built proa designed and built by a French
              engineer here in Texas. He had two carbon fiber professionally built
              dagger boards, one for each direction, deployed one at a time.... He
              had each daggerboard canted to windward some amount. A very beautiful
              and very fast boat. I have built one boat (Grok) with 2 asymmetrical
              leeboards. They were hollow and low aspect (elephant ear)although I did
              not choose to cant them because they were intended to work in several
              modes and I decided not to favor one mode.. JIB
              >

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

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







              [Non-text portions of this message have been removed]
            • graeme
              ... Did you mean canted or toed-in?
              Message 6 of 28 , Mar 27, 2013
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                > --- In Michalak@yahoogroups.com, "jhargrovewright2@"
                > <jhargrovewright2@> wrote:
                > >
                > > Nels, I understand the theory and agree that a asymmetrical leeboard
                > > canted to windward should help a sailboat but is there any data to
                > > back that up, that you know of.

                Did you mean canted or toed-in?
              • john colley
                We don t seem to be bothered with our centreboards ! Our boards are rarely straight down .Our yachts are ALWAYS Heeling.I cannot see where the problem is.  
                Message 7 of 28 , Mar 28, 2013
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                  We don't seem to be bothered with our centreboards !
                  Our boards are rarely straight "down".Our yachts are ALWAYS Heeling.I cannot see where the problem is.


                   
                  "There is magic in the feel of a paddle and the movement of a canoe, a magic compounded of distance, adventure, solitude, and peace."
                  -Sigurd Olson


                  ________________________________
                  From: graeme <graeme19121984@...>
                  To: Michalak@yahoogroups.com
                  Sent: Thursday, 28 March 2013 3:32 PM
                  Subject: [Michalak] Re: Twin Leeboards


                   


                  > --- In Michalak@yahoogroups.com, "jhargrovewright2@"
                  > <jhargrovewright2@> wrote:
                  > >
                  > > Nels, I understand the theory and agree that a asymmetrical leeboard
                  > > canted to windward should help a sailboat but is there any data to
                  > > back that up, that you know of.

                  Did you mean canted or toed-in?




                  [Non-text portions of this message have been removed]
                • graeme
                  You re talking about a canted board, ie. not being vertically upright in roll axis, leaning, heeling, flare, and etc, but was JIB talking about a different
                  Message 8 of 28 , Mar 28, 2013
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                    You're talking about a canted board, ie. not being vertically upright in roll axis, leaning, heeling, flare, and etc, but was JIB talking about a different performance angle altogether? Or maybe you're talking about a board being raked for 'n aft, no? I don't think JIB was talking about that. So was it board toe-in trying for better board/boat pointing in yaw axis, and better sheeting angle he had in mind?

                    --- In Michalak@yahoogroups.com, john colley <Helliconia54@...> wrote:
                    > We don't seem to be bothered with our centreboards !
                    > Our boards are rarely straight "down".Our yachts are ALWAYS Heeling.I cannot see where the problem is.
                  • jhargrovewright2@juno.com
                    Correct I meant toed in, rather toed out....terminology/words are important! ... From: graeme To: Michalak@yahoogroups.com
                    Message 9 of 28 , Mar 28, 2013
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                      Correct I meant toed in, rather toed out....terminology/words are important!

                      ---------- Original Message ----------
                      From: "graeme" <graeme19121984@...>
                      To: Michalak@yahoogroups.com
                      Subject: [Michalak] Re: Twin Leeboards
                      Date: Thu, 28 Mar 2013 04:32:03 -0000


                      <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">


                      > --- In Michalak@yahoogroups.com, "jhargrovewright2@"
                      > <jhargrovewright2@> wrote:
                      > >
                      > > Nels, I understand the theory and agree that a asymmetrical leeboard
                      > > canted to windward should help a sailboat but is there any data to
                      > > back that up, that you know of.

                      Did you mean canted or toed-in?







                      [Non-text portions of this message have been removed]
                    • daniel brown
                      can you explain how a leeboard canted to windward works better than a vertical one? To: Michalak@yahoogroups.com From: jhargrovewright2@juno.com Date: Thu, 28
                      Message 10 of 28 , Mar 28, 2013
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                        can you explain how a leeboard canted to windward works better than a vertical one?




                        To: Michalak@yahoogroups.com
                        From: jhargrovewright2@...
                        Date: Thu, 28 Mar 2013 12:31:35 +0000
                        Subject: Re: [Michalak] Re: Twin Leeboards





                        Correct I meant toed in, rather toed out....terminology/words are important!

                        ---------- Original Message ----------
                        From: "graeme" <graeme19121984@...>
                        To: Michalak@yahoogroups.com
                        Subject: [Michalak] Re: Twin Leeboards
                        Date: Thu, 28 Mar 2013 04:32:03 -0000

                        <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

                        > --- In Michalak@yahoogroups.com, "jhargrovewright2@"
                        > <jhargrovewright2@> wrote:
                        > >
                        > > Nels, I understand the theory and agree that a asymmetrical leeboard
                        > > canted to windward should help a sailboat but is there any data to
                        > > back that up, that you know of.

                        Did you mean canted or toed-in?

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






                        [Non-text portions of this message have been removed]
                      • jhargrovewright2@juno.com
                        That was an incorrect word choice. I was thinking toe in or out of the board not canted . Sorry. JIB ... From: daniel brown To:
                        Message 11 of 28 , Mar 28, 2013
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                          That was an incorrect word choice. I was thinking toe in or out of the board not "canted". Sorry. JIB

                          ---------- Original Message ----------
                          From: daniel brown <dannyb9@...>
                          To: "Michalak@yahoogroups.com" <michalak@yahoogroups.com>
                          Subject: RE: [Michalak] Re: Twin Leeboards
                          Date: Thu, 28 Mar 2013 18:51:49 +0000

                          can you explain how a leeboard canted to windward works better than a vertical one?




                          To: Michalak@yahoogroups.com
                          From: jhargrovewright2@...
                          Date: Thu, 28 Mar 2013 12:31:35 +0000
                          Subject: Re: [Michalak] Re: Twin Leeboards





                          Correct I meant toed in, rather toed out....terminology/words are important!

                          ---------- Original Message ----------
                          From: "graeme" <graeme19121984@...>
                          To: Michalak@yahoogroups.com
                          Subject: [Michalak] Re: Twin Leeboards
                          Date: Thu, 28 Mar 2013 04:32:03 -0000

                          <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

                          > --- In Michalak@yahoogroups.com, "jhargrovewright2@"
                          > <jhargrovewright2@> wrote:
                          > >
                          > > Nels, I understand the theory and agree that a asymmetrical leeboard
                          > > canted to windward should help a sailboat but is there any data to
                          > > back that up, that you know of.

                          Did you mean canted or toed-in?

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






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



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                          [Non-text portions of this message have been removed]
                        • graeme
                          ... JIB, I wasn t sure but thought so. IIRC you were asking,,, if there s evidence for it being any good? Assymetrical boards and toe-in? Asymmetric gives
                          Message 12 of 28 , Mar 29, 2013
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                            --- In Michalak@yahoogroups.com, "jhargrovewright2@..." <jhargrovewright2@...> wrote:

                            > Correct I meant toed in, rather toed out....terminology/words are
                            > important!


                            JIB, I wasn't sure but thought so. IIRC you were asking,,, if there's evidence for it being any good? Assymetrical boards and toe-in?

                            Asymmetric gives better specific performance than symmetric. Only stunt planes and the like have symmetric sectioned wings. The others use asymmetric sections. There's all sorts of specific asymmetric profiles, but a simple to make ovoid section (arc of circle one side, flat the other) works ok. Asymmetry - as Jim M notes on occaision: sails with their camber one side might get up to a CL of 1.5 but symmetric boards might only manage CL 1.0 (CL = coefficient of lift).

                            Toe-in? Yep, there's lots of evidence in theory and various practices for this improving boat performance - symmetrical dagger and centerboards leading edges angled and wedged to windward for each tack, hinged articulated keels or with trailing flaps to effectively reverse camber and get some 'toe-in', Dutch leeboard designs - the old style were tricked out for 0degrees running to 4 degrees of toe-in when beating by rake-variable cant-variable span-variable-twist, controlled by one rope - those are real interesting.

                            Toe-in is good and worthwhile if performance really does matter, but it's easily over done. Racers do it, fishermen wanting to be first in with the days catch to catch a good price, hungry watermen striving for a commercial premium or to pass clear of grounding danger did it.

                            Let's see if I don't get tangled up in asymmetric knots, with no guarantees. For beating to weather the overall leeway of the boat stays about the same whether the foil is toed-in or not. It might get a few degrees improvement in leeway is all. It stays about the same because the sum of the hull lateral resistance and the foil lateral resistance stays the same. Each source of lateral resistance still contributes the same individual amount to the combined total of leeway resistance. What toe-in changes is the pointing angle. The leeway angle may remain the same but the hull pointing angle can drop off the wind by the amount of angle that the foil is toed-in - and that, by reducing hull drag improves boat speed which may improve the amount of foil lift thereby maybe improving leeway angle again - a bit of a beneficial feedback spiral there - but the extra speed alone will improve vmg (distance made directly upwind over the ground). If you design board toe-in to vary continuously down from maximum when beating to zero angle running while raking the board back, as you do with a pivoting one anyway, then the board is optimised for lift/drag/speed at whatever point of sail. For some idea of what the Dutch boat wizards' leeboard idea is look at the continuously varying twist catering to varying apparent air speeds along a aeroplane propeller or a wind turbine blade and then pivot that blade off a sloping mount that also has a continuously varying caster angle!

                            Another thing that toe-in is used for is to improve sheeting angles on boats with difficult sheeting solutions; relatively narrow boats for their rig for example. Toe-in by improving pointing angle - allowing the boat to point a bit more away from the wind and more in the direction it is actually travelling through the water - gives a wider range of sheeting angle adjustment to get more drive from the sail which improves speed which may improve etc, etc,,, which again improves vmg.

                            Bookmarked these to grok long ago:

                            Remember Barend's insight into simple pythagorean and trigonometrically derived relationship shortcut tables he showed were inherent in nearly all boats made of sheet material and could be used by anyone. His 101 peice on Dutch leeboards is a wonderful thing:

                            http://www.duckworksmagazine.com/01/articles/leeboards/index.htm

                            http://www.eiseendenhof.nl/Friese-Reunie/Fotoalbum%20Friese%20Regionale%20Reunie%20Heeg%202004/Zondag%208%20augustus/index.html

                            http://www.eiseendenhof.nl/Friese-Reunie/Fotoalbum%20Friese%20Regionale%20Reunie%20Heeg%202004/Zondag%208%20augustus/index.html

                            http://www.vaartips.nl/


                            Graeme
                          • jhargrovewright2@juno.com
                            Graeme, I have been busy today....trying to get the dogs comfortable with their new home/facilities/yard.....so that I may start building boats again....after
                            Message 13 of 28 , Mar 29, 2013
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                              Graeme, I have been busy today....trying to get the dogs comfortable with their new home/facilities/yard.....so that I may start building boats again....after almost two years of turmoil and struggle after the fire. Life is good.Thank you for re orienting me to the leeboard tow in/out and the canting of the Dutch boats. You linked to a great site http://www.duckworksmagazine.com/01/articles/leeboards/index.htm You and he have convinced me " boards must have camber, caster and toe-in ". My 20' sailing canoe....that I will be building late summer will have two rather high aspect cambered leeboards. I will have to do some drawings to determine whether they will be weather or leeboards....toed in or toed out. I want to keep the leeboard and of course the pivot on the lee side out of the water when healing. Thanks for the Barend link.....I remember the article but needed the refresher....great insight and great presentation.
                              It took me a long time today to get through your post and the links. You have made me rethink the whole question. My canoe will be even better, thanks! JIB
                              ---------- Original Message ----------
                              From: "graeme" <graeme19121984@...>
                              To: Michalak@yahoogroups.com
                              Subject: [Michalak] Re: Twin Leeboards
                              Date: Fri, 29 Mar 2013 16:15:23 -0000


                              <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">


                              --- In Michalak@yahoogroups.com, "jhargrovewright2@..." <jhargrovewright2@...> wrote:

                              > Correct I meant toed in, rather toed out....terminology/words are
                              > important!

                              JIB, I wasn't sure but thought so. IIRC you were asking,,, if there's evidence for it being any good? Assymetrical boards and toe-in?

                              Asymmetric gives better specific performance than symmetric. Only stunt planes and the like have symmetric sectioned wings. The others use asymmetric sections. There's all sorts of specific asymmetric profiles, but a simple to make ovoid section (arc of circle one side, flat the other) works ok. Asymmetry - as Jim M notes on occaision: sails with their camber one side might get up to a CL of 1.5 but symmetric boards might only manage CL 1.0 (CL = coefficient of lift).

                              Toe-in? Yep, there's lots of evidence in theory and various practices for this improving boat performance - symmetrical dagger and centerboards leading edges angled and wedged to windward for each tack, hinged articulated keels or with trailing flaps to effectively reverse camber and get some 'toe-in', Dutch leeboard designs - the old style were tricked out for 0degrees running to 4 degrees of toe-in when beating by rake-variable cant-variable span-variable-twist, controlled by one rope - those are real interesting.

                              Toe-in is good and worthwhile if performance really does matter, but it's easily over done. Racers do it, fishermen wanting to be first in with the days catch to catch a good price, hungry watermen striving for a commercial premium or to pass clear of grounding danger did it.

                              Let's see if I don't get tangled up in asymmetric knots, with no guarantees. For beating to weather the overall leeway of the boat stays about the same whether the foil is toed-in or not. It might get a few degrees improvement in leeway is all. It stays about the same because the sum of the hull lateral resistance and the foil lateral resistance stays the same. Each source of lateral resistance still contributes the same individual amount to the combined total of leeway resistance. What toe-in changes is the pointing angle. The leeway angle may remain the same but the hull pointing angle can drop off the wind by the amount of angle that the foil is toed-in - and that, by reducing hull drag improves boat speed which may improve the amount of foil lift thereby maybe improving leeway angle again - a bit of a beneficial feedback spiral there - but the extra speed alone will improve vmg (distance made directly upwind over the ground). If you design board toe-in to vary continuously down from maximum when beating to zero angle running while raking the board back, as you do with a pivoting one anyway, then the board is optimised for lift/drag/speed at whatever point of sail. For some idea of what the Dutch boat wizards' leeboard idea is look at the continuously varying twist catering to varying apparent air speeds along a aeroplane propeller or a wind turbine blade and then pivot that blade off a sloping mount that also has a continuously varying caster angle!

                              Another thing that toe-in is used for is to improve sheeting angles on boats with difficult sheeting solutions; relatively narrow boats for their rig for example. Toe-in by improving pointing angle - allowing the boat to point a bit more away from the wind and more in the direction it is actually travelling through the water - gives a wider range of sheeting angle adjustment to get more drive from the sail which improves speed which may improve etc, etc,,, which again improves vmg.

                              Bookmarked these to grok long ago:

                              Remember Barend's insight into simple pythagorean and trigonometrically derived relationship shortcut tables he showed were inherent in nearly all boats made of sheet material and could be used by anyone. His 101 peice on Dutch leeboards is a wonderful thing:

                              http://www.duckworksmagazine.com/01/articles/leeboards/index.htm

                              http://www.eiseendenhof.nl/Friese-Reunie/Fotoalbum%20Friese%20Regionale%20Reunie%20Heeg%202004/Zondag%208%20augustus/index.html

                              http://www.eiseendenhof.nl/Friese-Reunie/Fotoalbum%20Friese%20Regionale%20Reunie%20Heeg%202004/Zondag%208%20augustus/index.html

                              http://www.vaartips.nl/

                              Graeme







                              [Non-text portions of this message have been removed]
                            • daniel brown
                              common practice when using two leeboards is to have the lee side board down in the water and the windward board up out of the water. whats the thinking
                              Message 14 of 28 , Mar 30, 2013
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                                common practice when using two 'leeboards' is to have the lee side board down in the water and the windward board up out of the water. whats the thinking behind keeping the lee board up and (presumably) the weather side board down?



                                To: Michalak@yahoogroups.com
                                From: jhargrovewright2@...
                                Date: Sat, 30 Mar 2013 02:40:51 +0000
                                Subject: Re: [Michalak] Re: Twin Leeboards





                                Graeme, I have been busy today....trying to get the dogs comfortable with their new home/facilities/yard.....so that I may start building boats again....after almost two years of turmoil and struggle after the fire. Life is good.Thank you for re orienting me to the leeboard tow in/out and the canting of the Dutch boats. You linked to a great site http://www.duckworksmagazine.com/01/articles/leeboards/index.htm You and he have convinced me " boards must have camber, caster and toe-in ". My 20' sailing canoe....that I will be building late summer will have two rather high aspect cambered leeboards. I will have to do some drawings to determine whether they will be weather or leeboards....toed in or toed out. I want to keep the leeboard and of course the pivot on the lee side out of the water when healing. Thanks for the Barend link.....I remember the article but needed the refresher....great insight and great presentation.
                                It took me a long time today to get through your post and the links. You have made me rethink the whole question. My canoe will be even better, thanks! JIB
                                ---------- Original Message ----------
                                From: "graeme" <graeme19121984@...>
                                To: Michalak@yahoogroups.com
                                Subject: [Michalak] Re: Twin Leeboards
                                Date: Fri, 29 Mar 2013 16:15:23 -0000

                                <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">

                                --- In Michalak@yahoogroups.com, "jhargrovewright2@..." <jhargrovewright2@...> wrote:

                                > Correct I meant toed in, rather toed out....terminology/words are
                                > important!

                                JIB, I wasn't sure but thought so. IIRC you were asking,,, if there's evidence for it being any good? Assymetrical boards and toe-in?

                                Asymmetric gives better specific performance than symmetric. Only stunt planes and the like have symmetric sectioned wings. The others use asymmetric sections. There's all sorts of specific asymmetric profiles, but a simple to make ovoid section (arc of circle one side, flat the other) works ok. Asymmetry - as Jim M notes on occaision: sails with their camber one side might get up to a CL of 1.5 but symmetric boards might only manage CL 1.0 (CL = coefficient of lift).

                                Toe-in? Yep, there's lots of evidence in theory and various practices for this improving boat performance - symmetrical dagger and centerboards leading edges angled and wedged to windward for each tack, hinged articulated keels or with trailing flaps to effectively reverse camber and get some 'toe-in', Dutch leeboard designs - the old style were tricked out for 0degrees running to 4 degrees of toe-in when beating by rake-variable cant-variable span-variable-twist, controlled by one rope - those are real interesting.

                                Toe-in is good and worthwhile if performance really does matter, but it's easily over done. Racers do it, fishermen wanting to be first in with the days catch to catch a good price, hungry watermen striving for a commercial premium or to pass clear of grounding danger did it.

                                Let's see if I don't get tangled up in asymmetric knots, with no guarantees. For beating to weather the overall leeway of the boat stays about the same whether the foil is toed-in or not. It might get a few degrees improvement in leeway is all. It stays about the same because the sum of the hull lateral resistance and the foil lateral resistance stays the same. Each source of lateral resistance still contributes the same individual amount to the combined total of leeway resistance. What toe-in changes is the pointing angle. The leeway angle may remain the same but the hull pointing angle can drop off the wind by the amount of angle that the foil is toed-in - and that, by reducing hull drag improves boat speed which may improve the amount of foil lift thereby maybe improving leeway angle again - a bit of a beneficial feedback spiral there - but the extra speed alone will improve vmg (distance made directly upwind over the ground). If you design board toe-in to vary continuously down from maximum when beating to zero angle running while raking the board back, as you do with a pivoting one anyway, then the board is optimised for lift/drag/speed at whatever point of sail. For some idea of what the Dutch boat wizards' leeboard idea is look at the continuously varying twist catering to varying apparent air speeds along a aeroplane propeller or a wind turbine blade and then pivot that blade off a sloping mount that also has a continuously varying caster angle!

                                Another thing that toe-in is used for is to improve sheeting angles on boats with difficult sheeting solutions; relatively narrow boats for their rig for example. Toe-in by improving pointing angle - allowing the boat to point a bit more away from the wind and more in the direction it is actually travelling through the water - gives a wider range of sheeting angle adjustment to get more drive from the sail which improves speed which may improve etc, etc,,, which again improves vmg.

                                Bookmarked these to grok long ago:

                                Remember Barend's insight into simple pythagorean and trigonometrically derived relationship shortcut tables he showed were inherent in nearly all boats made of sheet material and could be used by anyone. His 101 peice on Dutch leeboards is a wonderful thing:

                                http://www.duckworksmagazine.com/01/articles/leeboards/index.htm

                                http://www.eiseendenhof.nl/Friese-Reunie/Fotoalbum%20Friese%20Regionale%20Reunie%20Heeg%202004/Zondag%208%20augustus/index.html

                                http://www.eiseendenhof.nl/Friese-Reunie/Fotoalbum%20Friese%20Regionale%20Reunie%20Heeg%202004/Zondag%208%20augustus/index.html

                                http://www.vaartips.nl/

                                Graeme

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






                                [Non-text portions of this message have been removed]
                              • graeme
                                It can take a lot of concentration to visualise how the angle of toe-in changes as those leeboards are appropriately raked from aft to fully down to suit the
                                Message 15 of 28 , Mar 31, 2013
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                                  It can take a lot of concentration to visualise how the angle of toe-in changes as those leeboards are appropriately raked from aft to fully down to suit the point of sail. Probably a model would help.

                                  One thing not shown there is that the mount faces slope sort of wedge or cam-like... think of a short wide solid cylinder - a thick round block. Ok? To make a leeboard mount that changes the relative toe-in through a 0 to 2 or 4deg angle with rotation up or down from being parallel with the boat longitudinal centreline slice the block in half to make two round blocks only slope the slice a little. When the two blocks are rotated relative to each other the two inner sloping mating faces then will cause the outer block faces to change angle. The blocks don't have to necessarily be round. The original Dutch way I believe is to have that "slope" shaped by carving it into the top of the leeboard mounting face - not a lot of trouble considering how well the rest of the board is similarly shaped by carving. I've seen drawings of the block type mounts though, one attached to the side and it's mate to the leeboard. The pin or shaft, like the hole for the shaft, goes through the lot in a straight line (board, blocks, side, plank) that in plan and elevation views is straight but of course in end elevation view (body plan) for the Dutch boat types it has an angle normal (90deg right angle) to the slope of the tumblehome plank.

                                  http://www.duckworksmagazine.com/02/articles/bbwadvii/index.htm


                                  http://www.duckworksbbs.com/media/books/barend/index.htm

                                  http://www.punterwerf.nl/

                                  http://www.duckworksmagazine.com/02/articles/bbwadvi/part6.htm

                                  Graeme



                                  --- In Michalak@yahoogroups.com, "jhargrovewright2@..." <jhargrovewright2@...> wrote:
                                  > Life is good.Thank you for re orienting me to the leeboard tow in/out and the canting of the Dutch boats. You linked to a great site http://www.duckworksmagazine.com/01/articles/leeboards/index.htm You and he have convinced me " boards must have camber, caster and toe-in ".
                                  > It took me a long time today to get through your post and the links. You have made me rethink the whole question. My canoe will be even better, thanks! JIB
                                • jhargrovewright2@juno.com
                                  Graeme..... I do not understand it at all yet, but, the guy seems to have studied it inside out....today s Duckworks Mag.
                                  Message 16 of 28 , Apr 1, 2013
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                                    Graeme..... I do not understand it at all yet, but, the guy seems to have studied it inside out....today's Duckworks Mag. http://www.duckworksmagazine.com/13/howto/propulsion/index.htm#.UVmryr4o5LM appears to be calculating a way for the underwater foils....specifically the leeboard....to produce propulsion.....???? I will not comment until I can understand....grok..
                                    JIB
                                    ---------- Original Message ----------
                                    From: "graeme" <graeme19121984@...>
                                    To: Michalak@yahoogroups.com
                                    Subject: [Michalak] Re: Twin Leeboards
                                    Date: Mon, 01 Apr 2013 06:49:07 -0000


                                    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">


                                    It can take a lot of concentration to visualise how the angle of toe-in changes as those leeboards are appropriately raked from aft to fully down to suit the point of sail. Probably a model would help.

                                    One thing not shown there is that the mount faces slope sort of wedge or cam-like... think of a short wide solid cylinder - a thick round block. Ok? To make a leeboard mount that changes the relative toe-in through a 0 to 2 or 4deg angle with rotation up or down from being parallel with the boat longitudinal centreline slice the block in half to make two round blocks only slope the slice a little. When the two blocks are rotated relative to each other the two inner sloping mating faces then will cause the outer block faces to change angle. The blocks don't have to necessarily be round. The original Dutch way I believe is to have that "slope" shaped by carving it into the top of the leeboard mounting face - not a lot of trouble considering how well the rest of the board is similarly shaped by carving. I've seen drawings of the block type mounts though, one attached to the side and it's mate to the leeboard. The pin or shaft, like the hole for the shaft, goes through the lot in a straight line (board, blocks, side, plank) that in plan and elevation views is straight but of course in end elevation view (body plan) for the Dutch boat types it has an angle normal (90deg right angle) to the slope of the tumblehome plank.

                                    http://www.duckworksmagazine.com/02/articles/bbwadvii/index.htm

                                    http://www.duckworksbbs.com/media/books/barend/index.htm

                                    http://www.punterwerf.nl/

                                    http://www.duckworksmagazine.com/02/articles/bbwadvi/part6.htm

                                    Graeme

                                    --- In Michalak@yahoogroups.com, "jhargrovewright2@..." <jhargrovewright2@...> wrote:
                                    > Life is good.Thank you for re orienting me to the leeboard tow in/out and the canting of the Dutch boats. You linked to a great site http://www.duckworksmagazine.com/01/articles/leeboards/index.htm You and he have convinced me " boards must have camber, caster and toe-in ".
                                    > It took me a long time today to get through your post and the links. You have made me rethink the whole question. My canoe will be even better, thanks! JIB







                                    [Non-text portions of this message have been removed]
                                  • Anders Bjorklund
                                    Did you notice the date, John? On Mon, Apr 1, 2013 at 10:53 AM, jhargrovewright2@juno.com
                                    Message 17 of 28 , Apr 1, 2013
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                                      Did you notice the date, John?

                                      On Mon, Apr 1, 2013 at 10:53 AM, jhargrovewright2@... <
                                      jhargrovewright2@...> wrote:

                                      > Graeme..... I do not understand it at all yet, but, the guy seems to have
                                      > studied it inside out....today's Duckworks Mag.
                                      > http://www.duckworksmagazine.com/13/howto/propulsion/index.htm#.UVmryr4o5LMappears to be calculating a way for the underwater foils....specifically
                                      > the leeboard....to produce propulsion.....???? I will not comment until I
                                      > can understand....grok..
                                      > JIB
                                      >


                                      [Non-text portions of this message have been removed]
                                    • jhargrovewright2@juno.com
                                      Anders, I am not sure I understand the question....it is today s article in Duckworks Mag. Did you try the link? JIB ... From: Anders Bjorklund
                                      Message 18 of 28 , Apr 1, 2013
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                                        Anders, I am not sure I understand the question....it is today's article in Duckworks Mag. Did you try the link? JIB

                                        ---------- Original Message ----------
                                        From: Anders Bjorklund <andersbjorklund5@...>
                                        To: Michalak <Michalak@yahoogroups.com>
                                        Subject: Re: [Michalak] Re: Twin Leeboards
                                        Date: Mon, 1 Apr 2013 18:22:15 -0500


                                        <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
                                        Did you notice the date, John?

                                        On Mon, Apr 1, 2013 at 10:53 AM, jhargrovewright2@... <
                                        jhargrovewright2@...> wrote:

                                        > Graeme..... I do not understand it at all yet, but, the guy seems to have
                                        > studied it inside out....today's Duckworks Mag.
                                        > http://www.duckworksmagazine.com/13/howto/propulsion/index.htm#.UVmryr4o5LMappears to be calculating a way for the underwater foils....specifically
                                        > the leeboard....to produce propulsion.....???? I will not comment until I
                                        > can understand....grok..
                                        > JIB
                                        >

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







                                        [Non-text portions of this message have been removed]
                                      • graeme
                                        50% smoke
                                        Message 19 of 28 , Apr 1, 2013
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                                          50% smoke

                                          --- In Michalak@yahoogroups.com, "jhargrovewright2@..."
                                          > Graeme..... I do not understand it at all yet, but, the guy seems to have studied it inside out....
                                        • Anders Bjorklund
                                          The date of today s Duckworks article? April 1? No one noticed? On Mon, Apr 1, 2013 at 8:53 PM, jhargrovewright2@juno.com
                                          Message 20 of 28 , Apr 1, 2013
                                          • 0 Attachment
                                            The date of today's Duckworks article? April 1? No one noticed?


                                            On Mon, Apr 1, 2013 at 8:53 PM, jhargrovewright2@... <
                                            jhargrovewright2@...> wrote:

                                            > Anders, I am not sure I understand the question....it is today's article
                                            > in Duckworks Mag. Did you try the link? JIB


                                            [Non-text portions of this message have been removed]
                                          • graeme
                                            Ha !! It s April 2 already here obscured by the smoke haze fazed.
                                            Message 21 of 28 , Apr 1, 2013
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                                              Ha !! It's April 2 already here obscured by the smoke haze fazed.

                                              --- In Michalak@yahoogroups.com, Anders Bjorklund <andersbjorklund5@...> wrote:
                                              >
                                              > The date of today's Duckworks article? April 1? No one noticed?
                                            • jhargrovewright2@juno.com
                                              Anders, Thanks, you saved me some time. I was very busy yesterday so I printed it out so that I could read and study it....because I could not follow it. I
                                              Message 22 of 28 , Apr 2, 2013
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                                                Anders, Thanks, you saved me some time. I was very busy yesterday so I printed it out so that I could read and study it....because I could not follow it. I can study something difficult much easier if it is on paper. I picked it up this morning while fresh, to read it...... and realized I HAD BEEN HAD! JOKE ON ME. On the yahoo proa group there are a couple of members that are very hard to follow and have a lot of education and training in aerodynamics, engineering......so I save it and print it out then read and re read until it makes sense..... Dyslexia is a curse and a blessing. JIB
                                                <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> The date of today's Duckworks article? April 1? No one noticed?

                                                On Mon, Apr 1, 2013 at 8:53 PM, jhargrovewright2@... <
                                                jhargrovewright2@...> wrote:

                                                > Anders, I am not sure I understand the question....it is today's article
                                                > in Duckworks Mag. Did you try the link? JIB

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



                                                [Non-text portions of this message have been removed]
                                              • Tim Anderson
                                                I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow dagger
                                                Message 23 of 28 , Apr 4, 2013
                                                • 0 Attachment
                                                  I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots
                                                  that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow
                                                  dagger board for beating in shallow water. She pointed very high so long as
                                                  i sailed her as flat as possible. Tim P Anderson Swamp Dwelling Boat
                                                  Builder


                                                  [Non-text portions of this message have been removed]
                                                • jhargrovewright2@juno.com
                                                  Tim Anderson... I admire the Black Skimmer and the information. What swamp do you reside in? Can you add any comments experience with the bow dagger board.
                                                  Message 24 of 28 , Apr 4, 2013
                                                  • 0 Attachment
                                                    Tim Anderson... I admire the Black Skimmer and the information. What swamp do you reside in? Can you add any comments experience with the bow dagger board. That is an unusual place for a foil and I wonder how and why Bolger came up with that arrangement. Any info would be appreciated. JIB

                                                    ---------- Original Message ----------
                                                    From: Tim Anderson <naturalist71261@...>
                                                    To: Michalak@yahoogroups.com
                                                    Subject: [Michalak] Re: Twin Leeboards
                                                    Date: Thu, 4 Apr 2013 15:47:55 -0500


                                                    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
                                                    I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots
                                                    that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow
                                                    dagger board for beating in shallow water. She pointed very high so long as
                                                    i sailed her as flat as possible. Tim P Anderson Swamp Dwelling Boat
                                                    Builder

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







                                                    [Non-text portions of this message have been removed]
                                                  • John Trussell
                                                    I had a Dovekie with a bow centerboard. It worked fine in shallow water. It somewhat offset the lee helm which developed when I reefed. However, if you are in
                                                    Message 25 of 28 , Apr 4, 2013
                                                    • 0 Attachment
                                                      I had a Dovekie with a bow centerboard. It worked fine in shallow water. It
                                                      somewhat offset the lee helm which developed when I reefed. However, if you
                                                      are in the habit of heading up in a puff, be aware that the bow centerboard
                                                      will resist heading up-best to ease the sheet.



                                                      JohnT



                                                      _____

                                                      From: Michalak@yahoogroups.com [mailto:Michalak@yahoogroups.com] On Behalf
                                                      Of jhargrovewright2@...
                                                      Sent: Thursday, April 04, 2013 6:18 PM
                                                      To: Michalak@yahoogroups.com
                                                      Subject: Re: [Michalak] Re: Twin Leeboards





                                                      Tim Anderson... I admire the Black Skimmer and the information. What swamp
                                                      do you reside in? Can you add any comments experience with the bow dagger
                                                      board. That is an unusual place for a foil and I wonder how and why Bolger
                                                      came up with that arrangement. Any info would be appreciated. JIB

                                                      ---------- Original Message ----------
                                                      From: Tim Anderson <naturalist71261@...
                                                      <mailto:naturalist71261%40gmail.com> >
                                                      To: Michalak@yahoogroups.com <mailto:Michalak%40yahoogroups.com>
                                                      Subject: [Michalak] Re: Twin Leeboards
                                                      Date: Thu, 4 Apr 2013 15:47:55 -0500

                                                      <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
                                                      "http://www.w3.org/TR/html4/strict.dtd">
                                                      I had twin air-foiled lee boards on my PCB Black Skimmer, i used the pivots
                                                      that Phil used on Black Gauntlet with 1 degree toe-in. I also added a bow
                                                      dagger board for beating in shallow water. She pointed very high so long as
                                                      i sailed her as flat as possible. Tim P Anderson Swamp Dwelling Boat
                                                      Builder

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

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





                                                      [Non-text portions of this message have been removed]
                                                    • prairiedog2332
                                                      Jim drew a design called Eisbox that had a bow centreboard installed in the free-flooding bow well as an option. There is a cartoon in the files section. The
                                                      Message 26 of 28 , Apr 5, 2013
                                                      • 0 Attachment
                                                        Jim drew a design called "Eisbox" that had a bow centreboard installed
                                                        in the free-flooding bow well as an option. There is a cartoon in the
                                                        files section.


                                                        The idea was to lower it enough in shallow water to help prevent lee
                                                        helm as the leeboard was raised. Very simple to add as you don't have to
                                                        worry about sealing the case since it is already inside the
                                                        free-flooding well, so it can be a very shallow rectangular box open at
                                                        the top. The board is in the shape of a quarter circle about 18" in
                                                        diameter. Just needs some weight added so it stays down and a control
                                                        line leads from a tab added to the aft end leading up to a turning block
                                                        at the bow and then back to the helm to raise it to the desired height
                                                        and locked into a jam cleat.


                                                        Eisbox has a 5 ft. deep leeboard so as it is raised in shallows will
                                                        quite likely introduce lee helm and spoil upwind capability. So as the
                                                        leeboard is raised you lower the bow board and hopefully maintain a
                                                        neutral balance at the helm by adjusting both boards as you go along.
                                                        The only thing is that you are restricted to 6" draft on Eisbox as it
                                                        has a skeg ahead of the inboard rudder to protect it - which Jim doesn't
                                                        like all that much - but the fellow who commissioned it insisted on as
                                                        he wanted the OB to be mounted on the centreline. It was intended to
                                                        motor more than sail in the purpose he wanted a boat for. He wanted to
                                                        motor out offshore to fish when the winds were normally too low to sail
                                                        and sail back home when the on-shore breeze arose in the afternoon.


                                                        So a fellow like JIB might be interested in this information if used in
                                                        hull with less draft than Eisbox and likes to sail in the shallows?

                                                        Nels


                                                        --- In Michalak@yahoogroups.com, "John Trussell" <jtrussell2@...> wrote:
                                                        >
                                                        > I had a Dovekie with a bow centerboard. It worked fine in shallow
                                                        water. It
                                                        > somewhat offset the lee helm which developed when I reefed. However,
                                                        if you
                                                        > are in the habit of heading up in a puff, be aware that the bow
                                                        centerboard
                                                        > will resist heading up-best to ease the sheet.
                                                        >
                                                        >
                                                        >
                                                        > JohnT
                                                        >
                                                        >
                                                        >




                                                        [Non-text portions of this message have been removed]
                                                      • jhargrovewright2@juno.com
                                                        Nels, I was not familiar with Eisbox. Interesting boat. I did not find any info on the bow centerboard but have thought about the effects/uses that it might
                                                        Message 27 of 28 , Apr 6, 2013
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                                                          Nels, I was not familiar with Eisbox. Interesting boat. I did not find any info on the bow centerboard but have thought about the effects/uses that it might have. I think I understand the purpose and function balancing the boat in shallow water....Clever. I prefer to set up my boats with significant weather helm and rely on the rudder for a good portion of the LR.... I am just as careful building the rudder as the leeboard. I may do a centerboard again but, that is not on the list yet... Thanks for the information. That bow centerboard device has long been a mystery to me. Thanks, you have expanded my understanding of the sailboat, again.,,, I do love to sail in shallow water. At the Texas200 a couple of years ago in my Laguna....I stood on the bow of the boat....in the shade of the forward sail and followed the Matagorda Bay shore in 6" to 1' water sneaking up on the fish and other creature of the shallows. Interesting was that in displacement mode in 5"-6" the boat created a significant breaking 1/4 wave following off the transom. I was running directly down wind (10 mph) and did not have the push needed to plane. JIB
                                                          --------------
                                                          <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> Jim drew a design called "Eisbox" that had a bow centreboard installed
                                                          in the free-flooding bow well as an option. There is a cartoon in the
                                                          files section.

                                                          The idea was to lower it enough in shallow water to help prevent lee
                                                          helm as the leeboard was raised. Very simple to add as you don't have to
                                                          worry about sealing the case since it is already inside the
                                                          free-flooding well, so it can be a very shallow rectangular box open at
                                                          the top. The board is in the shape of a quarter circle about 18" in
                                                          diameter. Just needs some weight added so it stays down and a control
                                                          line leads from a tab added to the aft end leading up to a turning block
                                                          at the bow and then back to the helm to raise it to the desired height
                                                          and locked into a jam cleat.

                                                          Eisbox has a 5 ft. deep leeboard so as it is raised in shallows will
                                                          quite likely introduce lee helm and spoil upwind capability. So as the
                                                          leeboard is raised you lower the bow board and hopefully maintain a
                                                          neutral balance at the helm by adjusting both boards as you go along.
                                                          The only thing is that you are restricted to 6" draft on Eisbox as it
                                                          has a skeg ahead of the inboard rudder to protect it - which Jim doesn't
                                                          like all that much - but the fellow who commissioned it insisted on as
                                                          he wanted the OB to be mounted on the centreline. It was intended to
                                                          motor more than sail in the purpose he wanted a boat for. He wanted to
                                                          motor out offshore to fish when the winds were normally too low to sail
                                                          and sail back home when the on-shore breeze arose in the afternoon.

                                                          So a fellow like JIB might be interested in this information if used in
                                                          hull with less draft than Eisbox and likes to sail in the shallows?

                                                          Nels

                                                          --- In Michalak@yahoogroups.com, "John Trussell" <jtrussell2@...> wrote:
                                                          >
                                                          > I had a Dovekie with a bow centerboard. It worked fine in shallow
                                                          water. It
                                                          > somewhat offset the lee helm which developed when I reefed. However,
                                                          if you
                                                          > are in the habit of heading up in a puff, be aware that the bow
                                                          centerboard
                                                          > will resist heading up-best to ease the sheet.
                                                          >
                                                          >
                                                          >
                                                          > JohnT
                                                          >
                                                          >
                                                          >

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                                                          [Non-text portions of this message have been removed]
                                                        • prairiedog2332
                                                          As well as Dovekie and Black Skimmer Bolger added a bow board to his Whalewatcher for the same reasons - to help with helm balance. Bolger also tried to
                                                          Message 28 of 28 , Apr 6, 2013
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                                                            As well as Dovekie and Black Skimmer Bolger added a bow board to his
                                                            Whalewatcher for the same reasons - to help with helm balance.

                                                            Bolger also tried to develop a bow steering design, based I think on ice
                                                            boats? So a bow board you could adjust a bit to port or starboard would
                                                            probably be interesting like toed in or out with leeboards. I think the
                                                            control mechanisms quickly become complicated for the small gains in
                                                            performance. I think at planing speeds a bow board should be raised.

                                                            Nels
                                                            --- In Michalak@yahoogroups.com, "jhargrovewright2@..."
                                                            <jhargrovewright2@...> wrote:
                                                            >
                                                            > Nels, I was not familiar with Eisbox. Interesting boat. I did not
                                                            find any info on the bow centerboard but have thought about the
                                                            effects/uses that it might have. I think I understand the purpose and
                                                            function balancing the boat in shallow water....Clever. I prefer to
                                                            set up my boats with significant weather helm and rely on the rudder for
                                                            a good portion of the LR.... I am just as careful building the rudder
                                                            as the leeboard. I may do a centerboard again but, that is not on the
                                                            list yet... Thanks for the information. That bow centerboard device
                                                            has long been a mystery to me. Thanks, you have expanded my
                                                            understanding of the sailboat, again.,,, I do love to sail in shallow
                                                            water. At the Texas200 a couple of years ago in my Laguna....I stood on
                                                            the bow of the boat....in the shade of the forward sail and followed the
                                                            Matagorda Bay shore in 6" to 1' water sneaking up on the fish and other
                                                            creature of the shallows. Interesting was that in displacement mode in
                                                            5"-6" the boat created a significant breaking 1/4 wave following off the
                                                            transom. I was running directly down wind (10 mph) and did not have the
                                                            push needed to plane. JIB




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