5cm and 7cm stringers - "we must be stubborn!"

Although my last post was two months ago, I have been anything but idle. Most of that time was spent continuing the work on the stringers: first the 5 cm ones, then the 7 cm stringers. Along the way, I kept running into many of the same challenges I described previously—cutting dozens of notches, dealing with the considerable bending forces in the timber, and constantly correcting frames that wanted to move out of alignment.

Hull shape taking place!

A new problem also appeared. One of the 5 cm stringers snapped during what should have been its final dry-fit. It happened just as I was about to fasten it to a frame. After looking carefully at the broken piece, I came to the conclusion that grain orientation matters more than I had realised. It is worth examining a stringer from the side before installation and paying attention to how the grain curves through the wood. Ideally, those curves should follow the shape of the hull rather than work against it. Even so, I think bad luck played a role. That particular stringer had already been bent many times while I cut and adjusted the notches without showing any signs of weakness. My suspicion is that the way it was constrained by the screws during the final fit created a stress concentration that finally caused it to fail.

Fortunately, I had some spare timber intended for the upper stringers, so I used that stock to make a replacement. It only required scarfing together a new piece. The downside is that I will now need to produce additional stock for the upper stringers later on, but that seemed preferable to compromising on the current stage of the build.

New 5cm stringer (and new stem - don't miss my next post)

As more stringers were added, keeping the hull aligned became increasingly difficult. The growing network of timber members introduced new loads into the structure, and my strongback began to reveal its weak points. To identify them, I developed a simple test: firmly shake each frame in several directions and watch for movement. Whenever I found a section that flexed more than I liked, I added diagonal braces where they would be most effective. The result was a progressively stronger structure—but also one that resembled a giant spider web of temporary supports. Moving around the boat became an exercise in flexibility, requiring careful navigation between braces, clamps and frames.

Web of braces - getting hard to move around!

At least my notch-cutting technique improved considerably. I found that the multitool is excellent for making the initial cuts and relief cuts. A chisel can then quickly remove the larger sections of waste wood. After that, the rasp does the fine adjustment work. An angle finder also proved useful: by measuring the angle at which the stringer crossed a frame, I could compare it with the surface of the notch and immediately identify where more material needed to be removed. The process remained slow, but it became much more predictable.

Measure the stringer/frame angle

Check notch while cutting

The 7 cm stringers were actually the easiest of the lot. Their path through the frames is more straightforward, and the resulting notches are generally simpler to shape. After dealing with the more awkward geometry of the smaller stringers, these larger ones felt almost relaxing by comparison.

7cm stringers - the easiest ones

Week after week, I worked through the remaining notches. It became one of those jobs that seems endless while you're doing it, but eventually, almost without noticing, the pile of unfinished work starts shrinking. The yard owner would stop by from time to time and jokingly remark that "we must be stubborn." I remembered his warning that fitting the stringers would be the hardest part of the entire project. At the time, I thought he was exaggerating. Now I'm not so sure. In fact, I suspect the reality may be even harder than he remembered.

Of course, much of this difficulty comes from my lack of experience. If I had to build another hull tomorrow, I would almost certainly work faster and achieve better results.

So yes, I will continue stubbornly forward. The stringers are finally taking shape, and with every notch completed, the hull looks a little more like a boat.