Making Hardwood Lap Joint Boomerangs
By Dave Hendricks
Part Deux, Triblades and Quadriblades
Continuing with the knowledge we gained in Part One, we move on to the triblade. At the tablesaw, I set my miter gauge to 30 degrees. I then take two of the three pieces as described in part one, and cut the angle at one end of each as in photo 17. The third piece I leave at 0 degrees for a 90 degree cutoff. You now have three pieces for the boomerangs as in photo 18. Moving to the router table, I set the fence to allow about a 1/2" pass. This is shown in photo 19. I set the depth of the cut as in the traditional style boomerang. I make my cut the same way, but only need to make one pass for the width of cut. Make sure you cut the groove on the same side of both pieces. When this is done, and one piece flipped over the result should form the correct angle you need. Photo 20 shows both a pair of pieces with the laps cut and another pair with one piece flipped over and matched to the other. I may need additional passes to achieve the proper depth just as we did in part one. Once I have the two pieces cut to the proper depth, I mix the epoxy and glue them together.
Now it gets tricky. After the glue had dried, I unclamp the blank and clean up the glue that squeezed out. Sometimes this can be done with a wood chisel, other times I must use my random orbit sander. In photo 21 I am using the sander. You need a level surface on the blank in order to get a good cut with the router. Next I cut 60 angle at the elbow of the blank as in photo 22. In the photo you can see the plywood extension I have added to the miter guage. With shorter pieces, this is a big help. Notice that this blank would not even be on the miter guage without the extension. This cut is done at what I think is the proper amount and try to end up with a new edge about as wide as the third piece of wood, as in photo 23. I then go back to the router, which hopefully had the same settings as before, and cut a lap at the elbow of the blank and on one end of the remaining piece as in photo 24. Photo 25 shows all the pieces matched up and ready to glue.
Again it is time to mix more epoxy and glue the parts together. You can see why I try to make several of these at once to make mixing the epoxy worthwhile. A relatively small amount is good for several boomerangs.
When the blank is dry, remove the clamps and get out your pattern. I often use a Trifly or modification of one for the pattern. If you look closely at the blank you will notice that the joint lines are centered better on one side than on the other. I recommend using the side where they appear more centered as the top of the boomerang. By laying my pattern on top of the blank, and moving it around, I can get the best alignment of the pattern and blank. When satisfied with the alignment, I trace the pattern and cut out the final shape. See photos 26 and 27.
From here it is pretty much the same in the shaping and finishing of the boomerang as in Part One so I wonít re-hash that. Instead we go on to the tricky business of making quads.
Making quadriblade requires exact cuts but not exact measurements. In part one, I said we needed two pieces at exactly 2" x 12". That isnít quite so. As long as the two pieces are very close to that (1/16" off wonít hurt) but are identical in size, all is well.
This requires totally different routing from the previous boomerangs so pay attention and look at the photos. The first thing I do is mark the center of the pieces, lengthwise. Marking that, I try to center the second piece on top by its width. I mark approximately how wide I need my cut to be as in photo 28. I next clamp a fence to the router table at a location that will yield a cut just shy of the width needed. Router set up is in photo 29. I make my first cut, with a rather large pusher board, and then flip the piece 180 degrees and cut the same groove from the other end. The two grooves are shown I photo 30. I remove the material in between the cuts with a freehand "waste cut". I do the same thing to the other piece. The full width grooves are shown in photo 31.
Now it is time to check the fit. If I have done everything as planned, the pieces will not fit, as the groove cut is not wide enough. This is good. You can always remove more wood, but it is very difficult to put any back! I move the fence closer to the bit and make another cut. Sometimes it takes me several cuts to get it right, but by going slowly and making minor changes, you can prevent large errors. Remember to turn the pieces 180 degrees and cut from both ends. With careful work and some patience, you will achieve a perfect fit as in photo 32. Once the width of cut is perfect, donít forget to go back and adjust the depth of cut for a perfect match all the way around.
With both pieces ready, it is easy to spread some epoxy in the grooves and pop the two pieces together. Some of the ones I have made actually required a few taps with my mallet to get them to seat all the way. The joints were extremely close. When the glue is dry, get out your pattern (mine is a Gel Quad), trace, cut, shape and finish. Photo 33 shows a blank ready to trace the pattern.