I respect Laszlo's comment, and the designers and maunfacturers who implement them. I'll try to add some *off the top of my head* here...
When a supplier cuts a CNC kit, a puzzle joint is an easy matter as the programming and the cutter do all the work. For an amateur build, where the builder is cutting out the panels, a puzzle joint is an unnecessary complication, imho, unless the builder is *into it*, and that's fine too. Butt blocks or fiberglass splices will be plenty, *depending* on the program of the boat and the skill of the designer in placing them properly. And they are MUCH easier to implement. When the finish will be paint, you will be fairing anyway, and for some, a bright finished puzzle joint, well, it certainly will look *different*.
What are the advantages of a puzzle joint? More edge glue surface area, automatic alignment of *precut* parts, and might add some strength in the *plane* of the panel, but you again, may be glassing over that joint anyway. Conclusion, imho, they are a convenience in small lightweight CNC precut kits, for *some* builders who don't want to be bothered making three simple tick marks on the shop floor or shop bench before making a butt block or glass splice, or, for builder's who are *into the novelty of making such a joint successfully*, like an 8:1 or 12:1 scarf (usually no need for it with a well-designed composite glass-core-glass design). I'm an amateur, and I'm sure a professional advocate of puzzle joints could make my words look stupid and ignorant if they desired to do so. Yet, consider, a puzzle joint may make it more difficult to get a good and healthy quantity of epoxy filler blend into that tight joint, and cause it to be a dry or starved bond! The additional edge glue area on a puzzle joint can be a non-issue due to this potential for a starved bond, and as soon as there is a butt block, or glass tape, and a proper structural positioning of either, the starved bond is less likely an issue. Puzzle joints may be wonderful in those lightweight pre-cut kits for aiding in alignment
but I personally would not make the effort on a scratch built and cut build, nor would I personally want to risk a starved bond as epoxy gets soaked into the edge cuts (precoating would be recommended to prevent that). On the other hand, I am one who might do a puzzle joint for the novelty and challenge of it, and if I did, I would likely document it here, and communicate whatever issues I encountered. If it is already in the panel because one purchased a kit, then I agree with Laszlo... follow the recommended assembly procedures, particularly to make sure that the glue joint does not get starved, and I would likely do this with a serious precoating or two of the edges to be glued. Though a puzzle joint might be strong in the plane of the panel, I wouldn't want to have one right at a point where there is a high twisting load on that panel, without glass skins, especially without good precautions to avoid a starved bond. One reason why we as amateurs must trust the designers. We shouldn't draw up our own skiff and throw in a skinless puzzle joint just anywhere.
From one amateur to another, hope that helps.
Got any pictures Laszlo, or additional thoughts on your experience?
Swede, are you building a Bateau design? FL14? FS 14?