I mentioned this deep in a thread a while ago, but I figured I'd post it here again. I'm currently experimenting with 3D printing the cross-sections for a yostwerks skin-on-frame kayak. I decided on the Sea Cruiser 17-R, which has 6 cross-sections. I'm printing them in sections with ABS, then acetone-welding the half-lap joints together with screws as backup. I had to do a good deal of calibration to find a setting that allowed tight snaps on the tube, but it works very well now. I opted for 3/4" thickness, which feels nice and durable.

I created the models for the pieces in OpenSCAD, a parametric CAD software. I can punch in the offsets for any boat and it will generate the cross-sections. Cutting them into printable sections is unfortunately still mostly a manual process, but it's relatively easy -- just make the screw holes line up. I will post these files online somewhere once I make sure that this is a viable process.

I haven't put together the boat yet -- I need to visit a lumber yard to pick up wood for the strongback and I also need to order the vinyl skin. So, I don't know the durability of these sections yet. The total weight of all the plastic I used was just under 2kg, or two spools of plastic (~$60). However, I printied these relatively dense, since I don't know how durable they need to be. It's likely that they would work just as well with far less density. Since I have my own filament extruder, the plastic actually cost me closer to $6.

Here are a few more pictures:
https://i.imgur.com/iN47CcA.jpg
https://i.imgur.com/lAImifs.jpg
https://i.imgur.com/RTpRJi2.jpg
https://i.imgur.com/dINDiTN.jpg
https://i.imgur.com/oo2bGf3.jpg?1