2014-03-18

Post XIV - Stem and Stern Installation

I have been thinking about quite how to post this part of the build. It wasn't exactly straightforward, but I'll do my best to describe it. Sorry about the wordiness, but it's complex to put in words

I did my lamination late Friday night, in hopes that my epoxy would still be in somewhat of a green cure stage in the morning. Having the epoxy a bit soft still would keep my plane and spokeshave blades from dulling too quickly (so my thinking went). I have no idea if that is the proper thing to do, but that's how I did it and had no issues. I was about 4 whiskey drinks in the bag at that point, so I'm actually amazed it worked at all!

On to the woodworking

At Harry Bryan's hand tool course last fall, he and Wyatt taught us some techniques for cutting complex shapes out of wood. Their application was a small canoe paddle, but the principle is the same here

The stem plan is complicated. It calls for a rolling bevel reaching from inside to outside face, all along its curved length. There is also a narrowing of both inside and outside faces in the middle of the curve. At the bow it starts out as a wide, 60deg bevel with a broad inside and outside face, then tapers to a much steeper bevel with narrow inside and outside face at the sharpest part of the bend, then flares out again to a 45deg bevel with a broad inside face and narrow outside face.

Luckily, the sheet containing the stem plan was very detailed, so I was able to establish a centreline and mark out the nominal widths on both inside and outside faces before beginning my cuts It's tough to see in the picture above, but there is a centreline and a spline to either side of it.

Figure 38: Aft end of stem showing bevel, centrelines and splines on top



The planing operation seems daunting at this point, but the trick is to do only one "projection" at a time. I started by establishing the bevel between the edge of the inside face and the splines drawn to either side of centre on the outside face. I carried this all the way around the stem (even though I know the width of the inside face should be changing, but that comes later). The projection I'm completing here is a trapezoid shape with a gently rolling bevel and a projection axis parallel to the curving longitudinal axis of the stem piece.

Once I had that all done (with 0.5 mm or so to spare outside the lines) I flipped it on its side and worked with my blade perpendicular to the inside face, adding the hourglass-like projection on an axis perpendicular to the inside face at any point along it.

At this point, I had 2 projections done, and the stem cut down to my drawn lines on both inside and outside faces. Not done yet though - there is still some material to be removed. Because the projection axes were perpendicular, the offending wood stands out like a sore thumb. It appears as a ridge with tapering ends through the narrow section on the tightest part of the curve. At this point it's safe to forget about projections and plane away the ridge to create a flat bevel from inside to outside face all the way along.

Figure 39: The completed stem. It's hard to take a good picture that shows the rolling bevel and tapering.


Harry and Wyatt both use a pencil to get good results with this type of complex shape. Simply score a crosshatch over the area you want to work. As you pare away unwanted wood, the pencil marks get pared away too, and you can always see where you *didn't* plane. This is unbelievably helpful at keeping your plane or spokeshave on the correct angle and in making sure you don't pare away too much from one side or the other.

Last check after the you get "close as possible" to the desired shape is to run over the whole thing with a straight edge held against the bevel. This will reveal any remaining bumps or rounds that you might want to get rid of. Again, mark the raised areas with pencil and shave away carefully.


Stern

Last thing I did while a buddy was helping with a section of the stem was to cut out my transom piece. Nothing too special to report here. Edge glued (with epoxy and adhesive filler) 1" ash boards and transferred the transom pattern from the printed plans using carbon paper. Cut it out on my wobbly bandsaw. I was looking forward to making this part and it definitely doesn't disappoint! Gonna look cool when it's all planked in.

Figure 40: Transom piece roughed-in



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