A question about the Bolger Brick

Discussion in 'Boat Design' started by clmanges, Apr 4, 2021.

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  1. clmanges
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    clmanges Senior Member

    These are staples, then?

    I'll be patient for the rest; thanks!
     

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  2. sharpii2
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    sharpii2 Senior Member

    Yep.

    Imagine looking at it from a top view.

    In the last days of sail, these were often made of iron. So, they were literally giant staples.
     
  3. sharpii2
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    sharpii2 Senior Member

    Here's the sketches.

    I hope you can see that on a starboard tack the center of hull drag and the center of board drag line up with the center of lift of the sail (at least in this sketch). But on a port tack, there is a relatively large turning arm. To make up for that, the board on the starboard side (the side it will be on during a port tack) should be set further back.

    I hope this makes a little more sense to you now. I know it can get confusing. New Image.JPG New Image.JPG
     
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  4. clmanges
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    clmanges Senior Member

    Okay, I get that part now; thanks. I still can't completely figure out how you're attaching the board. The one line holding the fore/aft position is clear from your sketch, but I'm in the dark about the one holding the board against the hull, and how it automatically releases.

    BTW, "Mean Old Mr. Stump/Rock" would be a decent name for a band ... or maybe a seaside bar.
     
  5. sharpii2
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    sharpii2 Senior Member

    OK. See the two attachments.

    LB2.png LB2.png LB3.png

    The first shows the 'hook' design. As I hope you can see, the hook will only hold with horizontal tension. With any significant vertical component to the tension, the hook will release. The 'board will flutter away from the hull, held to the boat with only the fore and aft positioning line, which can then be used to retrieve it.

    The second attachment shows the top view of this arrangement. The handle of the lee board is made deliberately heavy. This is to keep the board from floating up. Its bottom can still float out from the hull until the wind pushes the hull against it. Being heavier on top also makes it easier to handle when shifting it from one side of the boat to the other.
     
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  6. clmanges
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    clmanges Senior Member

    Got it. And you've actually used this setup? I'd be worried about accidentally knocking it loose in moving around in the cockpit.
     

  7. sharpii2
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    sharpii2 Senior Member

    No.
    Not yet.
    I'm only about 65% sure this will work.
    If it doesn't, I may just mount the 'board on the starboard side on a pivot axel with lotsa washers, a suframe in the boat and a cap bushing on the outside of the board.

    This way, the board can pivot (only fore and aft) all the way up to the sheer line.

    I will then have to put up with less efficiency on the starboard tack.

    I have already built the rig for this boat. Hopefully, during this coming fall, I can build the hull, board, and rudder.

    It will all be built to work boat finish, as I'm mot inclined to sand and fill and sand and fill for hours on end, to get a flat shiny surface.
     
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