Internal Web for composite dagger board or wing mast?

Discussion in 'Multihulls' started by Slingshot, Jul 29, 2020.

  1. Slingshot
    Joined: Aug 2019
    Posts: 22
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    Location: South pacific

    Slingshot Junior Member

    How is the web joined to the 2nd skin on dagger board or wing mast? I saw a picture of a carbon dagger board that had 5 internal webs. That got me scratching my head. How would you build that.

    My guess would be:
    laminate both skins
    laminate the webs on one side
    flip the foil over and join the 2nd skin
    roll cloth through foil along web
    inflate bag to press cloth against web.

    Any other ideas?
     
  2. Chris Rogers
    Joined: Apr 2020
    Posts: 22
    Likes: 7, Points: 3
    Location: Boston, MA

    Chris Rogers Junior Member

    There are lots of ways! Some dagger boards are built with a mold only on one side so they get stacked up in stages with shear webs molded on other molds or over foam and then the top skin goes on top directly laid up over the internal structure. This is tons of work and requires very careful machining (or even more careful laminating and grinding!) and is very expensive. The problem with molding both halves and squishing together is that it is hard to control the bond-line where the shear webs meet the skins with all their longitudinal fiber. Your internal bag method is used too but it requires some fancy layup and bagging work.
     
  3. redreuben
    Joined: Jan 2009
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    Location: Beaconsfield Western Australia

    redreuben redreuben

    Shape foil from pvc foam, slice foam and laminate cut edges with DB, rejoin foam to reform board shape, glass externally with DB and carbon uni's at thickest point.
     
  4. patzefran
    Joined: Feb 2011
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    Location: france

    patzefran patzefran

    DB means ?
     
  5. redreuben
    Joined: Jan 2009
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    Location: Beaconsfield Western Australia

    redreuben redreuben

    Double Bias. +45-45
     
  6. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Most boards do not have an internal web.
    A fairly dense foam has enough shear strength to take the loads.

    Wing masts are a completely different animal and need engineering to decide what to do.
    It will depend upon your goals. If you want minimum weight and a given stiffness, experimentation would be a very expensive method.
    Probably also depends upon how large of a wing mast you want (compared to the total sail of the main.

    You might see if you can find a description of the old Gougeon wing mast plans, or try to contact the W17 designer - who offers a wing mast with his plans, but only if you succeed in building the hull.
    I don't think you can buy the W17 mast plans alone, but its been a while since I checked.
     

  7. oldmulti
    Joined: May 2019
    Posts: 965
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    Location: australia

    oldmulti Senior Member

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