Today I started mast construction. Earlier I talked about how I might build the main mast but I decided for sure after checking with the designer. The plans call for a solid mast of either spruce or substitutes such as douglas fir. Also the mast can be either a solid piece of wood or built up of scarfed together laminations. I chose douglas fir and laminations. Also the wood should be knot free and not have grain runouts. Also there should be at least 8 growth rings per inch of wood. I went to the store and bought some douglas fir planks that meet all these requirements. Since they were not long enough I had to scarf them together. The scarf is required to be 12:1 or greater. The following pictures show my attempts at cutting these scarfs.

The two scarfs on the right were cut with the tablesaw using the scarfing jig. They are uneven and of unacceptable quality. The problems come from the fact that the blade cannot cut through the entire width of the wood so two passes are required. Also it is difficult to hold the assembly totally flat and move it through the saw. Since the scarf jig is narrower than the wood it is also difficult to get the second pass to line up with the first. Back to the drawing board.

Here's a scarfing jig I built for my electric hand planer. I constructed it from cedar strips I rejected from my strip planking efforts. It has a platform to clamp the plank to and some angled guide rails to get the 12:1 slope for the scarf. The guide rails must be just far enough apart to allow the plank to slide in but the hand planer to span the width. After some experimentation I got the dimensions right. The notches are for C clamps to hold the plank fast.

I run the plane over the wood at a 45 degree angle. This minimizes edges being torn off but still allows use of the edge guides to determine the angle of the scarf. Also I try not to take off too much wood at one time. In just a few minutes I have a good scarf cut.

Here are some practice scarfs. They look a lot better but are not quite 12:1. I tweeked the angle of the guides to fix this.

Now I have a good scarf that is 12:1 and will take epoxy well. I have to cut 19 more like it.