Making the Stems

Rule #4.  ALWAYS make a pattern for complicated shapes.  Reason:  patterns are made from Not Cheap wood.  Boat parts are made from Very Expensive wood.  Make a pattern first to make sure the shape is right, before messing up a piece of Very Expensive wood.

Tammie Norrie has two stems, an inner and an outer.  The inner stem is what the planks will be glued to.  After the boat is planked, the outer stem will cover the edge of the planks, and serve as the surface that gets banged into the dock.

From the lofting, I traced the outline of the inner stem onto a piece of mylar, then made a pattern out of 1/4″ ply from the big box store.  The inner stem is specified to be 1-5/8″ thick, with a 3/4″ flat in the center.  The stem will be made in three layers; a 3/4″ center layer with a 7/16″ layer on either side.  Due to the curvature of the stem, each layer would have two pieces, but I would stagger the joints between layers for added strength.

Starting with the center layer, I cut two pieces of douglas fir slightly oversize, epoxied them together and screwed them to the pattern with a layer of wax paper between the two so I didn’t glue the stem to the pattern.  After the epoxy cured, remove the wax paper, screw the oversize stem back to the pattern and use a router with a flush-trimming bit to shape the stem to the pattern.  Repeat the process with the outer layers, except this time the flush-trimming bit follows the center layer.

One of the goals of lofting was to determine where the line for the bevel began on the stem.  This line is called the bearding line.  Cutting the stem bevel on the bench should be easier than trying to cut it after the stem is mounted.  The forward edge of the stem is nearly vertical, and the bevel line was as I expected.  The lofting showed me that the bearding line for the after portion of the stem (where it joins the keelson) was further back than I anticipated.  As this was my first attempt at lofting, I took a conservative approach, and cut the bevel close to the line on the forward portion of the stem, but stopped well short of the bearding line further aft.  I would finalize that bevel after the stem was mounted and I could verify the bevel when lining off.

2015-07-19 Rough shaping the inner stem
2015-07-19 Rough shaping the inner stem

In the picture above you can see the inner stem has been rough shaped with the bevel cut.  You can also see the plywood pattern I used for the stem.

While the inner stem is sawn and glued from douglas fir, the outer stem is laminated from ash.  Sometimes my approaches to the dock are a little more exciting than I intended; the laminated ash stem should be more resistant to dings.  The lofting was used to lay out the inner curve on a piece of 3/4″ MDF, with temporary blocks screwed to the MDF to mark the curve.  Strips of ash were milled 1/4″ thick, and then allowed to soak under a hot shower head for about half an hour.  The wet planks were then taken to the building table and clamped up, and allowed to set for a week.

DSCF1758
2016 01 24 Dry fitting the outer stem

Making the sharp bend of the stem is a challenge, which is why I soaked the strips.  After setting a week, the strips have dried and also taken a memory which makes the next step easier.

Take the assembly apart, cover the table and the cleats in plastic, and get every clamp you own (I only used a few clamps for the dry fit).  Laminating is a messy business and wet epoxy is very slippery, so dress for the occasion.  Allow the epoxy to cure for a week before you remove the clamps.

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