June 29, 2002

The safety-conscious among you will be saying, "Now what's he done with the blade guard on that table saw?

Never fear. There are situations where the blade guard is impossible. This is one of them We're going to be putting grooves down the front and back edges of the sides and on the top piece as well. When a saw cut doesn't go all the way through the wood, there's no way to keep a conventional blade guard in place. There are modern blade guards that avoid this problem, but I don't have one. 


Here's what we're doing on the table saw. The grooves in the sides and the top will receive the soundboard and the back of the harp. I think you can just make out that the groove on the front for the soundboard (on the left on the piece on the left) is a little wider. The saw kerf on my Ryobi BT-3000 table saw (with the blade that came with it) is just about an eight of an inch. The back material, an eighth-inch "walnut" plywood, is, if anything, a little shy of one-eighth inch thick, while the soundboard material, "eighth-inch baltic birch" plywood, is substantially bigger than 1/8 inch thick -- it's nearly 3/16".

 

The next photo shows how I dealt with that.


First, I unplugged that table saw!

I loosened the fence clamp and put the workpiece back down over the blade, with the blade in the slot that was previously cut. Then I put a metal ruler next to the work, and snugged the fence up against it. I tightened the fence down, removed the work and the ruler, plugged the saw back in, and made the cut again, the blade taking just another 3/64 or so on the inner wall of the groove -- the same as the thickness of the ruler.


The grooves in the top piece match up with those in the sides. Yes, I tilted the blade slightly to make the cut in the front side (the left side, here) of the top piece. You can see in this shot that the top piece also has its front edge angled back slightly to match the angle of the front of the soundbox. 



This is my favorite part so far. All these complex parts come together to make a recognizable shape. With all the power tools used on this project, my collection of saws, chisels, and knives is looking chagrined.


The soundbox members are screwed and glued together. The screws are what are usually known as wallboard screws! Did I mention that this beautiful dark wood is walnut? I did already mention how the grooves match up all around, which this picture was supposed to illustrate.


The soundboard doesn't quite fit, and needs to be planed down a little to slide in. It's cut from a 20x30 board of three-ply baltic birch plywood. I got two of these soundboards out of one sheet, with just scraps left over. 


Well, here's the "look at all those clamps" picture. Actually, there's a better one coming. In this one, a hardwood strip is being glued to the underside of the soundboard to provide a tougher backstop for the strings.  

This strip is walnut, and it came from in between the two side pieces (see photo). Nothing goes to waste.

You can see a notch has been cut out of the bottom of the soundboard -- this will accommodate the pillar passing through the soundboard without touching (i.e., damping) it. 

The string holes are then drilled through the soundboard and this rail. A hand-held drill would be all right for this. I used the drill press to avoid any wobbling that might make for a loose fit for the grommets that protect the soundboard from the strings.

A tip for folks who build from these plans: The first time around, I noticed that the string hole spacing on the plan was not consistent, varying from 7/8 to 1-1/8 inches. The measurements are not given on the plans. I figured it had something to do with varying string tension and vibrating envelopes. I folded the plans over on the centerline of the soundboard, and marked directly from the plan.  This time, I took more measurements and determined that the variations followed no pattern. The overall measurement from the top string hole to the bottom one is 28 inches, and there are 29 strings, so I simply laid them out one inch apart.


Here's the back -- same routine as the front (soundboard). On the prototype, I cut those oval holes out with a coping saw. What a pain. This time, I used a jig saw. A fifth the time, and only one chip-out. 


The grooves are smeared with glue and the back and soundboard are slid in. While the top of the box (not the soundboard, the top of the "frame") has the grooves in it, the bottom only goes between the back and front grooves, allowing the soundboard and back to slide in over it. The front of the bottom piece is angled to support the soundboard. 

The back and soundboard are held by glue in the grooves and reinforced with nails along the box bottom piece. The nails will be covered over by trim pieces front and back. Even all these little nails come in the hardware pack from Musicmakers!

Here the gap in the soundboard where the pillar will enter is filled along the bottom edge with the piece that came out of the notch. It, along with the soundboard bottom edge, will be trimmed off later.


Here the trim pieces are being glued over the nails. Except for trimming off the excess of the back and soundboard, the soundbox is complete. In the next installment, next weekend, I'll turn to the neck and pillar.

A harp -- a folk harp, at least -- is in many ways a lot simpler than a guitar. Apart from the strings and hardware, there are three pieces: soundbox, neck, and pillar. Again saving the installation and tuning of the strings, the soundbox is by far the most complex. The neck and pillar are each big chunks of solid (or laminated) wood, that merely have to be the right shape. There are some tricks to making a viable neck if you're not going to use manufactured plywood, and I'd like someone to tell me about them...just kidding, I mean, I think I have it figured out. And I will reveal all as I go forward here. Tune in Next Weekend  -- or if it's already next weekend (July 7, 2002), click "Next" below.

Time Today: 5 hours. Total so far: 9.5 hours

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Copyright 2002 Stephen Miklos