I’ve cut the panels, I’ve cut the stitches, now it’s time to get set up to assemble the hull. With some boat designs and construction methods, you start by building a “strong back” – a straight and stiff beam that is used to align the frames that determine the shape of the hull. The strong back has to be straight because it is the reference frame for the hull. And it has to be stiff so things won’t move as the hull is constructed.
For this hull, the panels define the shape, not frames. As a result, a strong back is overkill – a 2×4 would have worked. But I had a strong back from a previous boat, so I reused it.
Here’s a picture of the strong back with the stern and one of the bulkheads attached. The stern is necessary because it is part of the resulting hull. The bulkhead I attached could have been omitted – it is not part of the resulting hull. But this bulkhead helps support the panels as I stitch them together.
The bulkheads need to be square to the strong back. The bulkhead in the middle needs to be vertical relative to the strong back. The stern is at a 15 degree angle off of vertical (this is a parameter you can set in AVS Hull when you design the hull). To hold this angle, I cut a 2×4 at a 15 degree angle on my chop saw, then attached a small scrap of 2×6 to the beveled end of the 2×4. When this is clamped to the strong back, it holds the stern at the proper angle.
Since the top of the boat is not flat, the tops of the bulkheads can’t be placed directly on the strong back. When AVS Hull outputs the offsets for the bulkheads, it also shows how high off the strong back the bulkhead needs to be placed. I cut a scrap of plywood the correct width and used that as a spacer between the strong back and the bulkhead. For this particular hull, the bow is the highest point on the hull. As a result, the bow will rest on the strong back.
Here’s a picture of the stern setup (taken after I had attached a couple of panels). The 2×6 is screwed to the 2×4 to hold it in place. The 2×4 is clamped to the strong back, and the stern is clamped to the 2×6.
The panels will be attached to the stern (the stern is stitch-n-glued into the hull). The first panels need to be attached to the middle bulkhead to hold them in place while the next panels are stitched on. The remaining panels will not be attached to the middle bulkhead (it is not part of the hull).
In order to hold the first panels in place while attaching the stitches, I cut “L” shaped pieces from scraps of plywood and clamped them to the bulkheads. I also attached a clamp to the end of the “L”s on the stern to prevent the panel from springing off the end of the “L”. The center bulkhead did not need this because the spring tension held the panel against the bulkhead.
The pictures show spring clamps. After attempting to place the first panels, I replaced the spring clams with real clamps. The spring tension in the panel was enough that the spring clamps could not hold it in place.
Before placing the first panels, I stitched the bow together. This allowed the bow to rest on the strong back while the bulkheads held the rest of the panels in place.
Here’s a picture of the bow stitches (also shown in the previous blog post), and the panels positioned on the frame.
It’s starting to look like a boat!
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