Puzzle Joints!

This isn’t really a finished thing that I made but just sharing some puzzle joint success. This has had me really perplexed on the best way to do this.

I have plans to build some stitch and glue boats (I’ve built them in the past buy hand with portable tools) but really didn’t want to use butt joints. And the big professional boat kit makers use puzzle joints so I figured there has to be a way for us scrappy folks with far more limited funds to do it. And well, after a lot of tinkering I think we’re getting there.

I had some shifting of the cheap plywood due to the carpet tape so the joints are not super tight but we are heading in the right direction. Need to tighten up the hold downs and drop the offset back a hair.

Pretty amazed with the precision of this low rider 3 and some of my cobbled together parts.


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*by not buy…

And a little tighter joint.

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Whoops. Apologies for my post location.

Very nice!

Thanks! Fun stuff.

They look fabulous!

I would really love to see an intermediate inlay there too if you are going to clear finish it. Not because it adds anything to the build, just because I’d really like to see it! :rofl:

I am looking forward to seeing progress on the entire build I must say. It’s going to be very cool.

Please take the following with a grain of salt - it’s not intended to sway you from your current course, just adding my two cents worth of experience.

I think they use them to give amateurs a chance of perfect alignment. I’ve built dozens (figure of speech meaning half a dozen or so) of stitch and glue boats with surprisingly few photos to illustrate this!

In real life, while it’s easier to align, the puzzle joint is harder to keep fair than it looks. Using a butt strap rather than fibreglass over the inside joint will give you a much easier, perfectly fair joint.

(I would use a straight butt joint rather than a puzzle joint if I was going to paint it because it’s so much easier to keep fair, the puzzle joint doesn’t actually add any strength, and getting all that epoxy in the joint makes for a terribly messy glueup IMHO).

The following pics illustrate. Simple, with a perfectly fair result even with a slightly compound curve.


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Would half-lap puzzle joints be more easy and secure ?

I mean , they’d provide more gluing surface so probably a lot stronger, while keeping the alignement easy
Plus they’d be even easier to keep straight as the half lap would register the depth

Hi Peter. Many thanks for your reply and thoughts. I’m not offended at all and appreciate the input. Very cool on the multiple boat builds. A big reason for making the Low Rider 3 was to be able to cut panels for my designs drawn up in Freeship or similar basic CAD programs. I’m no expert in CAD stuff, just tinker.

An inlay is certainly a possible thing although my thoughts were to paint (hides more of my sloppy fingers).

Butt joints are certainly simpler to do. Cutting the puzzle pieces is something I’ve just been curious to do so we will see. I’ve tinkered with sail and power boats for decades and appreciate them both for their different uses. In the last couple of years I’ve gotten more into electric propulsion stuff; a good friend has built and modified some classic old Johnsons from the 50s, put a lot of design, and money, and time into his electric motors and it shows. They are basically Tesla outboards. His current one is on a 1960 Glastron and has a top speed of around 28mph; all electric. The boat is gorgeous. Our '67 Glastron has been powered by a couple electric motors that I’m still toying with. And there are some sailboats around the yard here too.

My current build is for a very simple almost dingy sized mini electric boat to test out the LR3’s capabilities in this area. I’ll certainly share my projects.

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An interesting thought. So many possibilities to chew on.

They aren’t as good in practice because the alignment of the surfaces has to be perfect and I’m not sure whether the cross-strength would be as good. With the butt join the lap is at worst one ply thickness with the butt strap taking the load off the joint itself. A scarf joint works similarly - spreading the load with no “hard” spots, but I think a half lapped joint will just create two “hard” spots.

Would be curious to test this.

They are calling this the double lapped puzzle joint.

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