Catamaran in stages - Scarf joints?

Discussion in 'Boatbuilding' started by MCP, Jul 7, 2019.

  1. MCP
    Joined: Aug 2018
    Posts: 13
    Likes: 3, Points: 3
    Location: South Africa

    MCP Junior Member

    Hi,

    I'm in the process of starting a build on a Easy Sarah 12m (40ft). I still need to identify the location for the build but the best option at this stage will only allow me to build her in stages.

    The construction of the Sarah is in stage anyways. You build the hulls, then the bridgedeck and bring everything together by extending the bulkheads over the bridgedeck.

    But due to my limited space I want to complete as much as possible before relocating to a place where I can bring the hulls and bridgedeck together.

    The bulkheads spanning over the bridgedeck calls for long continuous trusses.

    I've been studying the plans and I can go even further, with my limited space, if I can assemble the trusses in pieces with scarf joints. The design is such that the bulkheads connect with a single sheet ply from the hull to almost the centre of the boat. This is too wide for my space. But if can do a partial bulkhead that extends just a little over the hull and complete the remainder when I relocate.

    So my question is this: How strong is a well done scarf jointed truss versus a singular piece of wood truss?

    From my limited understanding (I've been trying to find info on this), a scarf joint is stronger than the wood itself?

    Maybe you experts can inform me please.

    I do not really want to deviate from the plans or compromise the structure.
     
  2. MCP
    Joined: Aug 2018
    Posts: 13
    Likes: 3, Points: 3
    Location: South Africa

    MCP Junior Member

    I did a quick rough drawing to better explain what I would like to do.

    The first drawing is the original construction method where the hulls are constructed with frames. Two sheets of ply, one in front of the frame and another at the back of the frame, are extended from the hull to the center of the boat to form a bulkhead. The bulkhead is further supported with two continuous trusses, one at the top of the bulkhead and the other at the bottom of the bulkhead.

    Drawing two: Instead of having a single sheet of ply extending from the hull and one continuous truss, I want to construct them in smaller pieces using scarf joints.

    Off course I will try and offset the joints and overlap them where I can.

    But the the question remains. How strong is a scarf joint compared to a singular piece of wood?
     

    Attached Files:

  3. upchurchmr
    Joined: Feb 2011
    Posts: 2,790
    Likes: 78, Points: 48, Legacy Rep: 579
    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member


  4. MCP
    Joined: Aug 2018
    Posts: 13
    Likes: 3, Points: 3
    Location: South Africa

    MCP Junior Member

    Hi,

    I do have a hard copy of Gougeon Brothers but have not had a chance to consult it. Thanks for the info.
    Will definitely go have a look.

    MC
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.