Wednesday, June 16, 2010

Gluing, stitching and more gluing

Because you can't ship 15 foot long pieces of lumber very economically the bottom and side planks, among other components, are composed of two pieces that have to be glued together.
Above can be seen the "puzzle joints of the nos. 1, 2 and 3 side planks after gluing. The shape of the joint makes it a lot easier to join the pieces with the proper alignment.

The stitching process involves drilling a 1/16th in. hole every 4 inches or so along both edges of the bottom and planks and the 3 supports. A 3.5 to 5 inch copper wire is pushed through the holes and hand tightened. Later all the wires are completely tightened with a pliers so all the pieces fit together as tightly as possible. As will be seen that doesn't always work out perfectly, so other methods are used.

Here I've stitched together the bottom and nos. 1 and 2 side planks and have added the upright supports.

All three side panels plus the bottom and supports are now stitched together and tightened as closely as I could. I had to move the stern support forward a small amount for a much better 3-dimensional fit. Some gaps can be seen between the front support and the port side and at the bow stem, but I'm told I can fix this with thickened epoxy later.

Here I'm tacking the bottom panel to the no. 1 plank and using a different mixture in a syringe to tack together between the side planks, avoiding getting epoxy on the wires. The big issue about working with epoxy is the cure time. This particular type needs 24 hours to cure at 75 degrees. For every 10 degrees less you need another 24 hours and you can't work under 55 degrees. In northern Wisconsin 75 degrees is hard to come by most of the year, so you have to compensate by providing a heat source or just waiting longer between steps.

All the tacking is now complete, the epoxy has properly cured and I can begin removing most of the copper wires.

Now I fill in the gaps between the epoxy tacks on the bottom and side tacks and let it cure again.

Monday, June 14, 2010

The boat I'm building is the Chesapeake Light Craft Skerry, the design of which is derivative of the small working sailboats of the British Isles. You'll have to go to the CLC website if you want to see what a finished Skerry looks like because their images are copyrighted. I liked the elegant look of it and appreciated the fact that it could be rowed as well. Having owned a 15 foot sloop rigged sailboat in the past I really liked the the Skerry's one-sail sprit rig for easy single handed use. So in early April I pulled the trigger and the kit was shipped to our lake house in NW Wisconsin, where I could make use of the garage as a workspace. The kit includes a 4x8' box with all the pre-cut wood components and a 2.2' box with the epoxy kit, fiberglass cloth, copper wire for stitches and other miscellaneous hardware. It's a kit so it's got to be easy, right? Will this be a "Scary Story" or a "Skerry Story"? Stay tuned.

Before I could begin I needed to buy and more importantly learn how to use some wordworking tools. I spent a couple of hours one Saturday morning in the Minneapolis branch of Rockler Woodworking learning the difference between a plywood block plane and planes for general use (the plywood one has a shallower angle of cut). The bottom plane in the photo is a rabbet plane for cutting a narrow groove in wood. I need to cut eight gains in various planks. A gain is a "descending rabbet" or one that goes from no depth on one end to full depth on the other. Both of these planes would have to be "tuned" (smoothing out the bottom surfaces with sandpaper) and the blades would have to properly sharpened before use, all of which took time. Who knew?

This is a wheel marking gauge for scribing a line parallel to an edge, a big help in positioning the seemingly hundreds of holes I had to drill for the wire stitches that held the pieces together until they are glued.

The bottom photo is of the two-part epoxy that can be used to attach fiber glass cloth, as a glue, as a wood filler or as a wood coating, depending on what and how much wood powder or silica is added.