Body, lines and sheer plans, oh my!

Unless you’re a boat builder, shipwright, marine architect or somehow otherwise involved in the marine industry, there’s every likelihood that you’re not familiar with body plans, lines plans and sheer plans.  But as a woodworker, you’d be well advised to get acquainted with them.

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The three plans, together, are generally referred to simply as “lines”.  Lines (formally called water lines) and sheer provide elevational and plan views.  Body plans provide sectional contours at various “stations” along the length of the vessel.  Traditionally, all three take advantage of the symmetrical nature of most vessels and are laid out as “half” plans.  The body plan, however, shows stations running for and aft from a common vertical centerline.

1812JamesMadison1807Lines

The body plan allows the loftsman to create templates for structural members.  By coordinating the dimensional information from all three plans (triangulation), curved pieces for structure or plating can be created.  In this regard, “lofting lines” is closely related to the layout methods used by traditional French framing carpenters, l’art du trait.  (For more about l’art du trait and traditional French carpentry, visit Patrick Moore’s website, historicalcarpentry.com)

An understanding of marine lofting methods or l’art du trait, will allow the amateur or professional woodworker to explore new design possibilities while working with complex curved or flat surfaces.

And, if for no other reason, an understanding of “lines” will allow you to build “half hull” models to be given to all of your boating friends.

Onkahye-Ship-Plan-Stern-cro

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4 Comments on “Body, lines and sheer plans, oh my!”

  1. Ron Says:

    Nice article Mr Laney, although you should have mentioned that is was/is the Loftsman who creates the faired body plan and Lines from the Naval Architects offsets, and once completly faired returns the offsets as finished/faired offsets, then the templates can be made.

    Regards,

    The Loftsman

    • D.B. Laney Says:

      You are absolutely right, Ron. And being reminded of the fairing process, I recall being told (only once) by my colleagues in the loft to “mind the weights and don’t step on the lines!”

  2. John LeBey Says:

    A good loftsman can lay out whatever these designers and naval architects come up with, but that bottom body plan seems a bit misguided. What in the world is that thing? Was it actually built? Couldn’t find a nice Herreshoff plan somewhere? Nice article, though.

    • D.B. Laney Says:

      It is the body plan of the U.S. Naval Schooner “Onkahye”. She was designed by Robert Livingston Stevens, commissioned in 1843, wrecked in 1848. The “Onkahye” design was radical and far ahead of its time. Naval historian Howard Chapelle (certainly a well known figure in the American Naval Architectural Community) considered her design to be the beginning of modern American racing yacht theory. At 95 feet, with two guns, she was a fast boat and my guess would be that she was good in light air. Apparently, there were many innovative features in the design, including sail chutes.


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