Making the First Cut

Progress continues on Frame B, and things are starting to feel real. Over the past few days, I finished marking all the lines on the MDF board. Using the GeoGebra diagram I created earlier, I carefully confirmed all the lengths and diagonals. Most of the measurements came out within 1 or 2 millimeters of the expected values—which, all things considered, is pretty good.

There are always small sources of error: the thickness of the pencil tip, slight parallax when reading measurements, and the fact that I’m working with just a 1-meter ruler. Anything longer than that becomes a bit of a juggling act. But even so, a 1–2mm deviation over lengths between 0.5 and 1.5 meters translates to a very low error percentage. I’m confident this level of accuracy is more than acceptable for a wooden boat like the Class Globe 5.80.

Frame B, cardboard knee joints

Since I still don’t have the wood for the outer edges of the frame, I shifted focus to the knee joints. These are the plywood reinforcements that will connect the frame members together. I started by experimenting with a cardboard template, placing it over the MDF frame drawing to see how it would fit—and it looked good! That gave me the confidence to move forward and mark the real knee joints directly on plywood.

Interestingly, Janusz (the designer of the Class Globe 5.80) recommends first building the wood frame edges, then making cardboard templates on top to shape the knees. But by using the measurements from the plans and the accuracy of the drawing on the board, I found I could safely reverse the process. This not only saves time, but keeps the build moving while I wait for the wood to arrive.

To make the job easier, I cut three 12 cm-wide strips from a 10mm plywood sheet to use as stock for the knees. And here comes the milestone: the first cut of the project! I used the boat yard’s table saw—with some guidance from the people there, who kindly showed me how to operate it safely and efficiently. It was a small step in terms of time, but a huge leap in terms of progress and confidence.

First cut!

I then marked the two types of knee joints I’ll need—four copies of each, to account for both sides of the frame and its symmetry.

Knee joint (not the most perfect one, but I got better)

In my next post, I’ll go into a bit more technical detail and explain how I used trigonometry to come up with an easy and accurate way to draw the knee joints directly on the plywood strips. Stay tuned!