Scarfs vs. Butt Joints

The puzzle joints used by CLC in their newer stitch and glue kits make panel alignment easy, but they are nearly impossible to make unless you are using computer controlled cutters. When we build from plans we are instructed to scarf the plywood sheets together. While scarfing makes a very strong joint, it's a lot of work and requires skill with planes and sanders. Could we just use butt joints? I built a Bolger Cartopper from 6mm okuome once, butting the panels together with thickened epoxy, reinforced on both sides with 4" wide strips of fiberglass cloth cut on the bias, with the glass strands diagonal to the joint, and never had a problem with the joints. It appears from the Pygmy website that their kits are assembled this way. Do we really need the extra strength (and work) of scarfed joints when we build kayaks from plans?

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RE: Scarfs vs. Butt Joints

Not sure of the relative merits on butt vs. scarf  for this application though there is no doubt that scarfing is stronger, I guess you could also back plate the butt on the inside though that could create curve issues.

I did see a post on this site of a builder who had his own puzzle jig built for use with a router, not as pretty as the puzzle pieces but reported that it worked. -

For me, I am planning on scarfing.  Not sure that I would want to be in rough seas with my but on relying on butt joints (sorry, could not resist ;)

RE: Scarfs vs. Butt Joints

Having built an Arctic Tern, which used butt joints on all hull panels (deck, sides & bottom), I gotta tell ya I think butt joints are just fine for S&G kayaks.  Glassed on both sides, then the final glassing inside and outside the hull makes for a plenty strong joint.  Good luck.  Jer

RE: Scarfs vs. Butt Joints

If you are going to use butt joints reinforced with glass, consider rounding or tapering the edges of the glass patches (oval shaped vice rectangular) so they aren't parallel to the butt and so they are staggered inside to outside.  That will let the panels take a fairer bend and be easier to blend for your finish.  And keep the glass away from areas where you will epoxy on sheer clamps and along inside edges of the keel and chines.  Then these seams won't have small bumps where the glass is.

RE: Scarfs vs. Butt Joints

This is good stuff. Thank you all for your feedback. I was hoping to hear from someone who had actually built a Pygmy boat, so especially appreciate Jerry's comment. It's apparent from your website that you are a highly experienced builder. I noted that you used narrow strips of glass and kept the strands aligned with the seam. Seeing your photos reminded me that when I butted the seams on my Cartopper, I sanded a slight bevel into the plywood on either side so the glass wouldn't create a bulge. My more recent experience building a Shearwater 17, with puzzle joints, taught me that the extra layer of glass is negligible, however, and disappears under the overall sheathing.

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