Stringers design

Discussion in 'Boat Design' started by Roni, Aug 4, 2020.

  1. Roni
    Joined: May 2020
    Posts: 21
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    Location: Brazil

    Roni Junior Member

    Hi there,

    I was just wandering are stringers in fiberglass sailboats always built in such a way as to follow buttock or waterplane lines (intersection between vertical or horizontal planes and the hull)? Or are "curved" stringers sometimes used? Are there flexible noam structural foams used for for molding stringers?

    I'm asking because I noticed that using the curved approach I could get a more even panel width, especially in the foward ones. In that way the scantlig required for each panel didn't vay so much between panels. With the straight approach wichts between panels vary more, and therefore scantling required.
     

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  2. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Realistically, for maximum strength to weight, stringers should follow a set of diagonals so as to be normal to the skin and standardize the panel size/scantling just like any other monocoque construction, e.g. cold moulded, welded metal, etc. Grid systems are used in modern FRP mass production or ply/cold mould home builds to simplify jigging, reduce moulding frames/parts, and pre-set engine bedding and outfitting.
     
  3. Roni
    Joined: May 2020
    Posts: 21
    Likes: 0, Points: 1
    Location: Brazil

    Roni Junior Member

    Thanks Jehardiman,

    For a V shaped bottom with a constant deadrise it seems that the grid system would be easy. In each section the bottom has the same deadrise, the foam mold for a tophat stiffener would be straightfoward, since section of the stringer would remain the same along the length of the vessel. However in a round bilge sailboat hull is that still the case? The hull section varies with the length, wouldn't following a diagonal with the tophat normal to the hull at each section be easirer? Placing a foam strip and then laminating on tope of it?
     
  4. jehardiman
    Joined: Aug 2004
    Posts: 2,729
    Likes: 332, Points: 83, Legacy Rep: 2040
    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Depends on the hull construction. For a one-off with a custom interior, build the hull with stringers then insert the outfitting. For mass production with a fixed interior layout, build the stringers into the liner, then set the liner into place. See this blog.
    FIBERGLASS BOATBUILDING: Internal Hull Structures - Wave Train https://wavetrain.net/2011/09/24/fiberglass-boatbuilding-internal-hull-structures/
     

  5. Will Gilmore
    Joined: Aug 2017
    Posts: 193
    Likes: 68, Points: 28
    Location: Littleton, nh

    Will Gilmore Senior Member

    Keeping in mind the purpose of stringers, to stiffen and define the hull shape, to hold the frames during construction and to provide "nailers" to aid in attaching planking or panels, you should put them any way that helps to perform those duties. There is nothing that says they should be placed in a set configuration except practically in strength, shape and construction.

    -Will (Dragonfly)
     
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