Change in elevation in stringer

Discussion in 'Fiberglass and Composite Boat Building' started by SeaJay, Apr 2, 2009.

  1. SeaJay
    Joined: Jun 2007
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    Location: Sacramento

    SeaJay Senior Member

    Hey guys/gals,

    I'm about to install the main stringers in my 46' motorsailer (bare hull). The stringers will be constructed per Gerrs' scantlings but I have a question that I haven't seen addressed in his books or elsewhere. While the main stingers will run continuously bow to stern, they need to change elevations several times to accommodate sole levels and engine mounts. My thought was to build angled "steps" to move from one elevation to the next. Generally I will have enough room so that the angle would not exceed 45 degrees and could be considerably less (more gradual). There will be unidirectional fabric continuously along the top of the stringers. David Pascoe makes a couple of comments about “doglegs” in stringers, and I can see from his examples that sharp discontinuities in the stringer are to be avoided but was wondering if anybody had any thoughts or suggestions about my plan before I start.

    Regards to all
     
  2. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    SeaJay,

    What do the plans show, stepping the stringers are possible of course, but it is not "normal" to do so......these ARE stringers you are talking about not longitudinal floor members....
     
  3. SeaJay
    Joined: Jun 2007
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    Location: Sacramento

    SeaJay Senior Member

    LL,

    No plans. This is a bare hull I purchased so I'm doing this myself. The first two stringers are each about 1 ft. port and starboard of the center line, and where they pass through the engine compartment, form the foundation for the engine mounts. At this point they need to be several inches taller than elsewhere, both for structural strength (according to Gerrs' scantlings), and because forward of the engine, they need to drop in order to accomodate the sole level of the forward cabins.
     
  4. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    OK, they are structural longitudinals...yeah same story applies treally, and yes you will have to step them as the show dictates.

    The step should not induce sharp corners or edges anywhere, the sole (floor) levels will dictate where the tops are to be, just remember the ply floor thickness.
     
  5. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    A 46 footer is a bit big to "just guess" the sizes mate, play around with Gerr's stuff, he is of course very good. Most scantling dimensions are designed for survey work, Gerr went between them and minimal dimensions and seems to have a nice balance of the show.

    Still have a gander at a boat being built in your area, if you cannot find any I can send you pics (email) if you need to see what we have done on boats around that size, there should be a boat being build somewhere that you can visit to see how it all goes together.
     

  6. SeaJay
    Joined: Jun 2007
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    Location: Sacramento

    SeaJay Senior Member

    LL,

    No guesswork involved. I've calculated these carefully and as you have suggested, compared them with simialar craft when I've been able to observe such. Nonetheless, I'd love to take a look at any examples you might be able to share. It's often the little details that get "thrown in" by experienced builders that escape clear discription in written instructions.

    Also, I had a related question that came up regarding Gerrs' scantlings used for the transverse floors at the keel area. After kicking it around a bit in this forum, we managed to get a comment from Gerr with an Errata & Update to his "Elements of Boat Strengths". Bottom line, and has been expressed elsewhere on these threads, Gerrs' scantlings appear to be fairly conservative and a very reasonable standard to shoot for.

    Thanks again for your input.

    Best Regards,

    SeaJay
     
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