This being Mother’s Day, 2006, I’d first of all like to wish all mothers the very best and say thanks for being you! Without you, we would not be here! Not too profound, but nevertheless very true.
In a previous entry, I mentioned the varying degrees of “fun” that one finds in constructiing the various components of a harp. The soundboard is a part of the harp that isn’t terribly visible, isn’t a great deal of “fun” to build, but is probably one of the most important elements of the entire project! As with the speaker cone of a set of fine audio speakers, it is the soundboard of the harp that, in my opinion, primarily determines the tone and volume of the instrument! While many makers are using various woods and wood combinations to build their soundboards, I am still sticking with sitka spruce which is still, I think, the most popular of soundboard woods and with which I’ve had excellent results. Here is my small collection of sitka — probably enough to build several harp soundboards.
While sitka spruce can be purchased from many sources, I have found the “Bargain Bag of Spruce” from Aircraft Spruce to be a good source of quarter-sawn soundboard material. These packs sell for $25 (plus about $25 shipping), and are random-sized pieces of fairly clear spruce. Occasionally one must trim a piece “with the grain” to be sure the grain is running true and horizontal, but it is generally pretty nice wood and it works well. For harp soundboards with the grain running horozontally, shorter pieces generally work very satisfactorily.
First, one must resaw the sitka spruce to proper thinness. To do this, one uses a resawing blade with the bandsaw.
The sitka boards are passed carefully thru the blade yielding thin pieces of wood. As you can see in the photo, I have my thumb curved in; these blades will cut thumbs as well!!
It is somewhat difficult to work with thin material using a wood planer as planers will sometimes turn thin wood into splinters. Instead, a gentler thicknessing can be accomplished using the “thickness sander” or “drum sander”. Mine is the Ryobi sander which has a sandpaper covered drum which spins. Below the drum sander is a motorized belt that draws the material under the drum, sanding the material to a given thickness. Sometimes numerous “passes” are necessary to achieve the desired thickness as only a small amount of material can be removed on any single pass. Here is the sander with the cover open.
Here is the sander with the lid closed. The black knob on the right adjusts the speed of the motorized belt, thus determining how quickly the wood will pass thru the sander. The port of the top of the cover is attached to a vacuum to collect the sawdust generated by this process.
When the sitka has been properly “thicknessed”, it is then roughly cut into angled pieces which will fit the harp soundbox. (The photo below is not of the French harp, but rather the replacement soundboard of my friend, Celia’s, harp and is somewhat wider than the French Harp soundboard. )
The adjacent edges of all the pieces are then “jointed” for tight fit, glue is applied, and they are clamped together on a wooden frame (below) to dry. This system is all from the genius of my harpmaker friend and mentor, Rick Kemper, and is a WONDERFUL system! The round, white clamps are actually pieces of 4″ PVC drain pipe cut into slices, and the frame is the approximate dimension of the finished soundboard. At the lower (wider) end of the frame are two sliding wedges. With the glue applied and the joints kept flat with the ring clamps, tapping the double wedge at the bottom drives the joints together. (This photo is also that of Celia’s harp soundboard.)
Having used this same system with the French Harp soundboard, here is what the sitka looked like after having been glued up. Note how much narrower it is than the frame as used above for Celia’s harp.
My latest “secret” (again, probably STOLEN from Rick Kemper) soundboard design is to taper the soundboard core from top to bottom and also from side to side. My goal is to make the soundboard thicker at the bottom, tapering to very thin at the top and also to make the board thicker down the center where the strings pass thru it, tapering to very thin at the edges. Once the sitka has been glued together, I then take a sander and carefully perform the tapering as I’ve described it. (Note that I am wearing a coat in this photo. Once again it is a photo of me tapering Celia’s soundboard this past winter.)
Those I consider the “better” builders will choose to use only solid sitka for their soundboards. To make this work successfully, they must place the soundboard into a drying chamber for a time before installation so that, once installed, atmospheric humidity will tend to “swell” the wood. If this is not done (as I’ve learned from experience), soundboards will dry out in winter when in heated room conditions and will develop horizontal cracks! Rather than be a sitka soundboard purist, I have adopted a laminate approach to building soundboards. My soundboards are made of three layers: an inner layer of vertical grain veneer, a core of horizontal grain sitka, and an outer layer of vertical grain veneer. In this instance, I am using maple veneer on the inside, book-matched walnut veneer on the outside with a core of sitka spruce.
On the left you can see the roll of veneer tape which is used to hold the various pieces of veneer together until it is glued to the substrate material (in this case, the sitka core). You can see a single strip of tape holding the two halves of walnut veneer sheets together above on the right. In like fashion, the maple inner veneer is held together in the same way on the left. I use a fabric cutting wheel to do most of the veneer cuts. Here is the making of the inner veneer in progress.
The triangular “waste” pieces are then turned end for end and attached to the lower edge of the veneer sheet to make the lower end wide enough. With the three components of the soundboard prepared and cut to shape, I then use this “Better Bond” veneer glue from Joe Woodworker to attach the veneers to the sitka core. Better Bond is a powdered resin that becomes usable when mixed with water. While the container says “cleanup with water”, I’ve learned to use it with disposable containers, stirrers, spreaders and to wear rubber gloves when using it! Cleanup is nearly impossible as it sticks to everything!!
Incidentally, I am not a financial person and certainly not a “Certified Public Accountant” as stated on the photo above. Somewhere I have come upon a piece of foam board that has this writing on it. It makes for a nice, semi-soft work surface. By placing this on my cast iron table saw top, I find I cause fewer “dings” to my woodworking projects.
SO, after spreading the Better Bond glue onto the sitka core, I then let it sit for 15 minutes, place the veneer on the glue, and place it into the vacuum press to dry. What you see here is a plywood “caul” atop the veneer which evenly distributes the pressure of the vacuum over the veneer.
On top of the “caul” is a sheet of white fabric which serves to facilitate air flow to the suction tube in the center when the vacuum pump is turned on. To prevent the caul and other surfaces from being glued fast as well, I use sheets of regular kitchen Cut-Rite waxed paper. Here is another view of the vacuum apparatus showing the vacuum pump arrangement I have put together.
Better Bond takes 4-6 hours to dry in 70 degree temps. The vacuum apparatus has a vacuum-operated switch on it which turns the pump on and off as needed to maintain the vacuum for the prescribed time.
I have decided to make the thickness of this soundboard thinner than ones I’ve made in the past in an effort to compensate for the fact that this soundboard is considerably narrower than my other harps. This is an effort to get as much tone and volume as possible from the narrower soundboard. The board has been made only 3/16 inch thick at the bottom tapering to a mere 3/32 inch at the top. One can only hope that one’s choices will be appropriate and that the thinner board will withstand the harp’s string tension. Here is the outside, walnut veneer-covered surface of the soundboard after having been removed from the vacuum bag. Note that, even though the grain is not exciting, I have attempted to do what is called “bookmatching” to make the veneers look very similar on each side of the center line.
Here is an edge view of the soundboard, showing the three elements of the lamination. Below you see the maple veneer, in the middle is the end grain of the quarter-sawn sitka spruce, and on the top is the walnut veneer. Once the soundboard is installed, you will not be able to see these laminations. This edge will be covered by a strip of walnut trim.
Here is the soundboard standing against the “soundbox, thus far”.
The next process will be that of making and attaching the string ribs to the soundboard, installing “liners” to the soundbox to broaden the gluing surface of the sides, then actual installation of the soundboard.