Stringers Finally in Place

With all the notches finally completed, the next task was to dry-fit all the stringers into their final positions. After months of bending, adjusting and repeatedly testing the fit on the frames, I already suspected that the alignment of the frames was no longer perfect. The forces involved in bending the stringers are considerable, and over time they had inevitably pushed some parts of the structure out of position.

Stringers finally in their final positions!

I removed all the stringers and started the alignment process again from the beginning. It became a bit of a back-and-forth exercise: I would align the frames, install some stringers, observe how the bending forces affected the structure, then adjust and repeat. Eventually, I found a process that worked well for me.

Aligning the frames (again)

The first step was aligning each frame with the next one. For this, I used the laser level aligned with the centre markings I had previously made on the strongback beams. The strongback had proven to be a very stable reference, which made these markings extremely valuable. With the laser projecting the centreline, I adjusted each frame until it was correctly centred above it.

I then checked the spacing between frames, making sure it matched the distances specified in the plans. At the same time, I verified that each frame was vertical using a bubble level. To check that the frames were perpendicular to the centreline, I placed my speed square against the face of the frame and visually aligned its perpendicular edge with the centreline projected by the laser on the floor.

Checking distance between frames

Once a frame was correctly positioned, the next challenge was making sure it stayed there. The supports holding the frames to the strongback needed to be very solid, so I kept adding cross braces wherever I detected movement while testing the structure. Frames D and D1 were particularly challenging, as this is where the hull curvature becomes more pronounced. The stem was also difficult because the stringers need to rotate slightly as they transition into the bow. My bending tool proved very useful here, allowing me to apply controlled force without damaging the timber.

Cross brace spaghetti

Even with everything reinforced, some movement was unavoidable when adding the stringers. When you think about it, bending a stringer creates a large lever force acting on the frames, with the notches acting as pivot points. Every time a stringer was bent into position, it was effectively trying to pull the frames out of alignment.

The 3 cm stringers were the easiest ones to install, especially the horizontal ones along the sides of the hull. They require relatively little bending, and each one added noticeable stiffness to the overall structure. As more stringers were attached, the hull gradually became less flexible and easier to work with.

I worked from stern to bow, installing stringers on both sides alternately. This helped balance the forces and avoid loading one side of the structure more than the other.

Next came the 5 cm stringers along the sides. These were more challenging, especially the lower 5 cm stringers, which require significantly more bending. I left those for last, when the structure was already much stronger and better able to resist the forces involved.

The 7 cm stringers were comparatively straightforward. By that point, the hull structure was already quite rigid, and the remaining adjustments were much easier. I was no longer checking every frame centreline with the laser level before each step, as at that stage there was limited ability to make large corrections anyway. Still, after everything was installed, I believe the final alignment came out very well.

Good alignment

I asked some of the experienced boat builders at the yard whether they were able to achieve perfect alignment when building their boats. Their answer was reassuring: there are always a few millimetres of variation here and there. One of them told me a saying from the previous master boat builder at the yard: "once you place your frame, never look back." Another one was: "he who looks from one side cannot see the other." They made me laugh, but there is definitely some practical wisdom behind them. At some point, you need to trust your measurements, accept small imperfections, and continue moving forward.

View from the bow

After a long and demanding process, I finally have all the stringers in place. There is still some preparation work before the permanent glue-up, but the structure is now ready for the next major step.

I can't wait to start covering these stringers with plywood. This has been one of the most difficult stages of the build so far, and seeing the hull gradually take shape makes all the effort worthwhile.