Mosshead

gluing butt joints

September 28th, 2006

Okay, so I thought I was going to keep an in-progress journal about building the kayaks, but I was too tired at the end of the day to keep up on it.

After reading through a couple of forums, particularly Dan’s journal at West Coast Paddler’s I went out and bought Moore’s Kayaks You can Build which covers the Pygmy Coho. In the book, Moores suggests only gluing the butt joints on 1 side.

The issue is aesthetic - taping and gluing the butt joints on the outside means that there will always be a slight bump at the butt joints as well as a higher potential for messing up with the scraper when cleaning up.

On my boat, we’d already glued both sides. The epoxy had to be scraped to bring down high points and feather the edges. Unfortunately, I had a standard scraper and its edges tore into the plywood which was a real PITA to fix. I went out and bought a better carbide-tipped scraper and that made all the difference in the world.

If you’re building a boat, I would say that the carbide tipped scraper was one of the most important tool purchases I could have made. The other most important tool purchase was 3 good rasps. I’ll probably write later about tools since I’m kind of a gearhead anyway.

So, we got the right scraper which made a world of difference on the second boat which we only glued on one side. I decided that the experimental boat #1 would be mine.

Cleaning up the excess from the edges of the plywood strip was best done with a rasp, not a razor blade. I’m sure that if we were to build another boat, we would use a lot less epoxy in the butt-gluing step. It ended up taking us most of the first week just doing the butt joints and then cleaning them up. I had numbered the mylanar with a sharpie pen to make it easy to reuse on the second boat, but half of the mylanar pieces were placed ink-side down which … transferred to the wood and had to be sanded out. We were very lucky that the ink didn’t travel all the way to the wood. Note to self: don’t use ink that contains alcohol (i.e. Sharpies).
In any case, suffice it to say that gluing the butt joints helped me temper my cavalier approach to building the boats and in the end was a harmless lesson. All mistakes were fixable, just more work.

Here are my tips for this step:

1. Follow Moore’s suggestion and glue butt joints on the inside only. Just be sure that when moving the strips around, you fully support the joints.
2. Pay close attention to how much epoxy you’re using. You really don’t need much to float the tape.
3. When you put down the mylanar, make sure that you squeeze out all the air. Air bubbles create a lot of clean up and probably compromise the structure if you get any air bubbles in the joint.
4. Use as much weight as you can get on it. Our clay bricks weren’t heavy enough. We filled up yogurt containers with sand and placed those on top of the bricks. Diving and fishing weights worked best.
5. Invest in a carbide tipped scraper and good rasps. I paid $15 for the scraper at Home Depot. Our local hardware shop had better quality rasps than Home Depot. I paid $24 each for 2 larger sized rasps and $12 for a small rasp.

Entry Filed under: pygmy sea kayaks