Butt joints are a lot easier to make than scarfs. They are not as strong, but are normally more than adequate for our purposes. Because of the extremely tortured curves on the WD12, though, they could snap during construction. Another option is to use butt joints reinforced with a three or four inch wide strip of 4mm plywood on the inside. I used this method on a sailing skiff 20 years ago and it works well. It gives you the strength of a scarf with the ease of construction of butting. -Wes

I should also have mentioned that, while helping my daughter build a Ganymede, I butted the cut pieces together on my kitchen floor because it was too cold in my shop. You can see pictures and detailed instructions at http://twofootartist.com/ganymede-construction-notes/ -Wes

I'm working on a Wood Duck 12 from plans and used butt joints and they are fine (it's all together, just waiting for final cloth/epoxy on deck). The Pygmy boat kits are put together with butt joints, so it's not an uncommon idea. 

Make sure that you use a piece of fiberglass tape on both sides of the butt joint, and sand to smooth and to feather the edges of the tape.  If you need more info on how to do this, there are lots of posts on the forum, or ask and we can talk you through the process.

Or you can watch the Pygmy YouTube video (http://www.youtube.com/watch?v=b-IsUwQdzFg&list=PL532F00547A3F55F7&index=3&feature=plpp_video)

Kathy

We should also mention that the cloth you use on the joints should be cut on the bias - that is, with the threads running diagonally to the seam - for maximum strength. And don't use fiberglass tape, as the bound edge will leave a ridge that you will have to grind off later. -Wes

Very timely comment Wes. I just glued together the hull panels on another Shearwater last night with fiberglass tape. This morning I removed the clamps and saw that it looked, er, bad. Quick work with a heat gun and the sander took it off and I reglued some bias cut 4 oz glass. A much nicer result.

Dan

Dang it Dan, I wish I had known. I would've posted that hint a day sooner. -Wes

After MUCH deliberation I too used butt joints to join 2x8 sheets of Okoume for my SW 17 build. Then transferred the lines from the plans using Saral transfer paper. So far things have worked great. I wet out a 6" and 3" wide strip of glass and layed it on the inside joints. I did not do the outside because it will get glass in the end, but it sounds like the Duck may have some more challenging curves? Just cut the hatches out today....as soon as I figure out how to post a pic I will do so.

I am curious: just how much weaker is a butt block than a 12 to 1 scarf?

I'm no idealogue when it comes to scarfs or butts or puzzle joints.  I deploy whichever best suits the scenario.  You'll find all three in CLC boats.  We use puzzle joints in about 80% of the kit boats these days, scarf joints in the others, with a few using 'glassed butt joints.  Chesapeake kayaks still have decks joined amidships with butt joints backed with wooden blocks.  (The wooden plate scheme is very very strong, but the butt blocks interfere annoyingly with interior fiberglass sheathing.)  For plans builders we advocate scarf joints or 'glassed butt joints.  

When discussing strength, it is not very helpful to compare strength in absolute terms.  If the weakest approach---'glassed butt joints---gives you 600% of the strength needed, but you never actually exceed 110%, then it's academic that a puzzle joint gives you 700% and a scarf joint yields 800%.  They are ALL more than strong enough, so the premise of the question is misleading.  Better to talk about which is easier for the builder. You cannot beat puzzle joints for accurate panel alignment, for example, but you need a CNC machine to cut them...  

My experiance: Butt joints backed with a ply block are butt ugly, so only use them when the inside blocked side is hidden. Butt joints with fiberglass tape - cut from cloth or tape with selvage edge snipped off - are good, but do require some fairing (scraping & sanding) to look decent. Scarfs - 8:1 or wahtever your choice - are my fav, but require attention when lining up to get a nice smooth alighnment. CNC puzzle joints are a snap, literally. Grease them up with epoxy and snap them together = done. Puzzle joints should have one or both sides glassed whereas I have built boats with bare scarf joints. Summery, I think scarf joints are the strongest, but any one of those scenerios is strong enough since break test will break the plywood panel somewhere other than the joint.  Yes, I have busted test joints for giggles.

OK, I really tried but this thread has gone on so long that I can't resist any longer.

Laszlo

and there's the puzzling joint...

Love it

The scarf joints are much nicer looking than the butt joints. 

And the puzzle joints look pretty cool (at least that's what everyone says when they see them on my kayak)

When [2 foot] speaks of totured twist and turns on the wood duck 12 he is not exagerating. The duck was my first project and with the plan option I was concerned that the skarf would be strong enough and that the pressures of the bends would respond differently at the skarf joints and cause a dip or bulge at those points. The skarf proved to be the stongest part of the ply material.

That said if this this is your first attempt at building I would strongly suggest that you take advantage of the technology and experience that CLC has put into their product and not try to reinvent the wheel on your first project. The above suggestion to add materials to beef it up are all wrong asthetically and practically when the curves and grace of the duck is factored in--in my opinion.

You are about to invest time, money, and give a statement about yourself in the workmanship of your project---is that all worth the gamble of a butt joint........CZ

Was just curious.  If anyone does run across the answer, please post it.  It would allow us to answer the only relevant question, 'does it matter?' which John hinted at.