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Cutting the sheer line

Discussion in 'Strippers, Stitch-n-Glue, and Other Wood Composite' started by Chipper1959, Jan 16, 2012.

  1. Chipper1959

    Chipper1959 Curious about Wooden Canoes

    I'm building a Hiawatha and I'm starting to wonder about how I'm going to cut the strips along the sheer line at each end.......they curve up quite a bit from station 3 to station 6.
    I'm assuming they're cut before the fiberglass goes on ?? there a secret to ensuring that the curve on each side is the same ?
    I was thinking of trimming one side, and tracing that line onto a sheet of paper then using that as a template for the other side.
  2. Todd Bradshaw

    Todd Bradshaw Sailmaker

    I usually trim the sheer line after the outside glass goes on, after the outside glass is filled and sanded, after the inside sanding and glassing are done and after the gunwales are installed (though I might rough-cut it, oversized a bit, to make gunwale installation easier). It's difficult to glass neatly up to a finished edge. Once the gunwales are on, you sand the hull down to its final level, even with the gunwale tops.

    As for getting both sides even - anything that works is good.
  3. Rod Tait (Orca Boats)

    Rod Tait (Orca Boats) Designer/Builder

    If you glass the outside and then roll the whole thing over with forms still inside you can mark on the inside where the sheer line is, remove forms and then use a long batten to mark the sheer line. Cut a little above the line so you can install gunwales after glassing inside and trim down as previous post suggests.
  4. Canoez

    Canoez Paddle Bait

    Just before I glass the outside of the boat, I use an underscribe gage to transfer the sheer height from the forms (Don't forget the bow and stern height!) to the outside of the hull as a pencil mark. I do this at each station on both sides of the boat. Once the hull is glassed, I take a long spline batten (usually a strip that isn't cove-and-beaded - kept for it's good grain and uniform flex) and clamp it so that it goes through the pencil marks at the station locations. I then use a utility knife to score the glass on the outside of the hull. I then take an old, relatively trashed Dozuki blade and put it in my Z-Saw and cut the sheer at the score line - with a little practice, you can make it follow the curve with ease. I use the "trashed" blade because the glass is hard on cutting tools.

    This leads to a symmetric sheer that follows the designer's intent. When attaching gunwales and decks, I leave the cut line about 1/16" proud of the gunwales to sand the hull down to the gunwales.

    If you've not marked the hull before , get the hull to sit upright by making sure the bow and stern are both plumb and keep the hull that way. Lay out your sheer line with masking tape down the side of the boat using a spline batten. This let's you check the shape and fair of the sheer before you mark with a utility knife and cut as above. Once this is done, use a level that goes athwartship (Perpendicular to the Keel-line!) and shim until level sitting on the top of the strips. Then use a pair of dividers to transfer a measurement from the marked side of the boat to the unmarked side of the boat using the top of the level as a reference. Repeat at multiple locations along the length of the boat -as many as you need to reproduce a decent curve. This is more work than just taking the sheer line off the forms, but if you don't have a good sheer as part of the forms, it's the easy way.

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