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Re: Twin Leeboards

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  • 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 1 of 28 , Mar 29, 2013
      --- 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 2 of 28 , Mar 29, 2013
        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 3 of 28 , Mar 30, 2013
          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 4 of 28 , Mar 31, 2013
            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 5 of 28 , Apr 1 8:53 AM
              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 6 of 28 , Apr 1 4:22 PM
                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 7 of 28 , Apr 1 6:53 PM
                  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 8 of 28 , Apr 1 10:12 PM
                    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 9 of 28 , Apr 1 10:26 PM
                      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 10 of 28 , Apr 1 11:57 PM
                        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 11 of 28 , Apr 2 5:55 AM
                          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 12 of 28 , Apr 4 1:47 PM
                            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 13 of 28 , Apr 4 3:17 PM
                              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 14 of 28 , Apr 4 3:30 PM
                                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 15 of 28 , Apr 5 5:19 PM
                                  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 16 of 28 , Apr 6 6:37 AM
                                    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
                                    >
                                    >
                                    >

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



                                    [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 17 of 28 , Apr 6 11:32 AM
                                      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




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