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Re: Twin Leeboards

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  • 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 1 of 28 , Apr 5 5:19 PM
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      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 2 of 28 , Apr 6 6:37 AM
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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
        >
        >
        >

        [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 3 of 28 , Apr 6 11:32 AM
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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




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