Making the Stem Knee

With the hull framework essentially complete, the next task was to build the stem knee—the solid timber that ties together the stem, the bottom of the hull and Frame E. 

The stem knee

I began by cutting a section from one of my pine boards and using the bandsaw to split it into two pieces with a rough approximation of the final shape. These were then glued together and, after curing, passed through the planer until I reached the required 40 mm thickness.

Cutting two pieces with a rough shape

Glue-up of both pieces

Removing thickness to get to 40mm

The next challenge was determining the exact shape of the knee. Two surfaces were straightforward enough: the angle where it joins the stem and the contour of the hull between the stem and Frame E. The difficulty was transferring those complex shapes accurately to the timber.

At that point, I remembered an excellent YouTube video demonstrating a technique known as a Tick Stick, and decided to give it a try. The first step was to place a rectangular piece of plywood in the correct longitudinal plane between the stem and Frame E. I then searched around the boatyard for a small scrap of wood—there is never a shortage of those—and made my own Tick Stick. One end was shaped into a sharp point for locating reference points, while the sides were cut with a series of distinctive notches using the table saw and bandsaw. Those irregular shapes are the secret that allows the stick to be repositioned accurately later.

The plywood sheet used for marking the points

The process is remarkably clever. For each reference point, the pointed end of the stick is placed against the shape being copied while the side of the stick rests against the plywood panel. I then traced the outline of the stick onto the plywood. Repeating this operation at many different locations creates a collection of unique reference marks.

Point the tick stick, draw its outline on the plywood

Once enough points had been recorded, I removed the plywood panel and laid it flat on a workbench over a sheet of cardboard. Working in reverse, I aligned the Tick Stick with each traced outline and marked where its pointed end landed on the cardboard. Joining all those points with a pencil produced the complete template. I cut it out with scissors, brought it back to the boat... and it fitted perfectly on the very first attempt. Whoever invented the Tick Stick was a genius.

Place the tick stick on top of each marking, draw the corresponding point

With the cardboard template complete, transferring the shape onto the prepared pine blank was easy. Now came the challenge of cutting it accurately.

The edge that joins the stem is perfectly straight, so I cut it on the table saw using the sacrificial MDF guide I described in an earlier post. The edge following the hull bottom has a slight curve, so I used the bandsaw, deliberately leaving a couple of millimetres outside the line. I'll bring it to its final shape later when fairing the hull before fitting the bottom plywood.

The most difficult feature was the inside corner formed by two intersecting straight cuts. The problem is that a table saw blade is circular, so it cannot stop precisely at an internal corner, while the bandsaw doesn't produce perfectly straight cuts over that distance. I eventually came up with a method that combined both tools.

I marked perpendicular reference lines crossing at the inside corner on the timber and also drew a corresponding reference line on the table saw insert, directly in line with the blade. By carefully advancing the workpiece until both markings aligned, I could stop the cut at exactly the right point. This produced two very accurate cuts, leaving only the small circular section created by the blade radius. I then moved to the bandsaw, made several relief cuts into that remaining waste, removed the bulk of it with a chisel, and finished the corner with a rasp and file. 

Cutting almost to the inside corner

Relief cuts near the corner

Removing the excess wood on the inside corner

The final job was fitting the knee into the boat. The inside corner required further adjustment because of the V-shaped junction formed by the two lower stringers at the stem. I initially worked on this with the multitool and a chisel, slowly removing material and checking the fit repeatedly. It worked, but progress was rather slow.

One of the boatyard staff noticed what I was doing and introduced me to a tool I'd never seen before, but with a funny name: a Plaina Guilherme. The literal translation into English would be something like "William Plane", although its proper name is a shoulder plane. Unlike a conventional plane, it allows the blade to work right up against a vertical face, making it ideal for trimming material at the bottom of a corner. It turned out to be exactly the tool I needed. Within minutes I had refined the V-shaped recess and achieved a much better fit than I could have managed with the chisel alone.

The "Plaina Guilherme" (who was this guy?)

The stem knee is now ready to be installed. I just need to source some longer screws that can pass through the thickness of the stem and reach the knee on the opposite side. Once those arrive, fitting it should be straightforward.

After so many months of measuring, cutting, shaping and dry-fitting, the boat is finally approaching another major milestone. The permanent glue-up of the hull structure is now just around the corner.